diff --git a/appData/templates/blank/project.gbsproj b/appData/templates/blank/project.gbsproj
index 15d5db6c7..7a00eb2a0 100644
--- a/appData/templates/blank/project.gbsproj
+++ b/appData/templates/blank/project.gbsproj
@@ -2,7 +2,7 @@
     "name": "___PROJECT_NAME___",
     "author": "___AUTHOR___",
     "_version": "4.0.0",
-    "_release": "1",
+    "_release": "3",
     "scenes": [],
     "backgrounds": [
         {
diff --git a/appData/templates/gbhtml/project.gbsproj b/appData/templates/gbhtml/project.gbsproj
index 704a51e84..add1c8a50 100644
--- a/appData/templates/gbhtml/project.gbsproj
+++ b/appData/templates/gbhtml/project.gbsproj
@@ -2,7 +2,7 @@
     "name": "___PROJECT_NAME___",
     "author": "___AUTHOR___",
     "_version": "4.0.0",
-    "_release": "1",
+    "_release": "3",
     "scenes": [
         {
             "id": "94c18861-b352-4f49-a64d-52f2e3415077",
diff --git a/appData/templates/gbs2/project.gbsproj b/appData/templates/gbs2/project.gbsproj
index e2e42037c..4270165e3 100644
--- a/appData/templates/gbs2/project.gbsproj
+++ b/appData/templates/gbs2/project.gbsproj
@@ -2,7 +2,7 @@
     "name": "___PROJECT_NAME___",
     "author": "___AUTHOR___",
     "_version": "4.0.0",
-    "_release": "1",
+    "_release": "3",
     "scenes": [
         {
             "id": "94c18861-b352-4f49-a64d-52f2e3415077",
@@ -4728,8 +4728,14 @@
                             {
                                 "command": "EVENT_REPLACE_TILE_XY_SEQUENCE",
                                 "args": {
-                                    "x": 22,
-                                    "y": 6,
+                                    "x": {
+                                        "type": "number",
+                                        "value": 22
+                                    },
+                                    "y": {
+                                        "type": "number",
+                                        "value": 6
+                                    },
                                     "tileIndex": {
                                         "type": "number",
                                         "value": 0
@@ -4746,8 +4752,14 @@
                             {
                                 "command": "EVENT_REPLACE_TILE_XY_SEQUENCE",
                                 "args": {
-                                    "x": 22,
-                                    "y": 17,
+                                    "x": {
+                                        "type": "number",
+                                        "value": 22
+                                    },
+                                    "y": {
+                                        "type": "number",
+                                        "value": 17
+                                    },
                                     "tileIndex": {
                                         "type": "number",
                                         "value": 4
@@ -4764,8 +4776,14 @@
                             {
                                 "command": "EVENT_REPLACE_TILE_XY_SEQUENCE",
                                 "args": {
-                                    "x": 4,
-                                    "y": 11,
+                                    "x": {
+                                        "type": "number",
+                                        "value": 4
+                                    },
+                                    "y": {
+                                        "type": "number",
+                                        "value": 11
+                                    },
                                     "tileIndex": {
                                         "type": "number",
                                         "value": 0
diff --git a/src/lib/compiler/scriptBuilder.ts b/src/lib/compiler/scriptBuilder.ts
index 922275aa6..3e43751f0 100644
--- a/src/lib/compiler/scriptBuilder.ts
+++ b/src/lib/compiler/scriptBuilder.ts
@@ -2142,7 +2142,11 @@ extern void __mute_mask_${symbol};
     );
   };
 
-  _getTileXY = (addr: ScriptBuilderStackVariable, x: number, y: number) => {
+  _getTileXY = (
+    addr: ScriptBuilderStackVariable,
+    x: ScriptBuilderStackVariable,
+    y: ScriptBuilderStackVariable
+  ) => {
     this._addCmd("VM_GET_TILE_XY", addr, x, y);
   };
 
@@ -5205,8 +5209,8 @@ extern void __mute_mask_${symbol};
   };
 
   replaceTileXYScriptValue = (
-    x: number,
-    y: number,
+    x: ScriptValue,
+    y: ScriptValue,
     tilesetId: string,
     tileIndexValue: ScriptValue,
     tileSize: "8px" | "16px"
@@ -5219,43 +5223,134 @@ extern void __mute_mask_${symbol};
     const tileIndex = this._declareLocal("tile_index", 1, true);
 
     this._addComment(`Replace Tile XY`);
-    const [rpnOps, fetchOps] = precompileScriptValue(
+
+    const [rpnOpsX, fetchOpsX] = precompileScriptValue(optimiseScriptValue(x));
+    const [rpnOpsY, fetchOpsY] = precompileScriptValue(optimiseScriptValue(y));
+    const [rpnOpsTile, fetchOpsTile] = precompileScriptValue(
       optimiseScriptValue(tileIndexValue)
     );
-    const localsLookup = this._performFetchOperations(fetchOps);
-    const rpn = this._rpn();
-    this._performValueRPN(rpn, rpnOps, localsLookup);
-    rpn.refSet(tileIndex);
-    rpn.stop();
-    if (tileSize === "16px") {
-      // Top left tile
-      this._replaceTileXY(x, y, tileset.symbol, tileIndex);
-      // Top right tile
-      this._rpn() //
-        .ref(tileIndex)
-        .int8(1)
-        .operator(".ADD")
-        .refSet(tileIndex)
-        .stop();
-      this._replaceTileXY(x + 1, y, tileset.symbol, tileIndex);
-      // Bottom right tile
-      this._rpn() //
-        .ref(tileIndex)
-        .int8(tileset.width)
-        .operator(".ADD")
-        .refSet(tileIndex)
-        .stop();
-      this._replaceTileXY(x + 1, y + 1, tileset.symbol, tileIndex);
-      // Bottom left tile
-      this._rpn() //
-        .ref(tileIndex)
-        .int8(1)
-        .operator(".SUB")
-        .refSet(tileIndex)
-        .stop();
-      this._replaceTileXY(x, y + 1, tileset.symbol, tileIndex);
+
+    if (
+      rpnOpsX.length === 1 &&
+      rpnOpsX[0].type === "number" &&
+      rpnOpsY.length === 1 &&
+      rpnOpsY[0].type === "number"
+    ) {
+      // Can optimise using constant values for X and Y coordinates
+      const localsLookup = this._performFetchOperations(fetchOpsTile);
+      const constX = rpnOpsX[0].value;
+      const constY = rpnOpsY[0].value;
+      const rpn = this._rpn();
+      this._performValueRPN(rpn, rpnOpsTile, localsLookup);
+      rpn.refSet(tileIndex);
+      rpn.stop();
+      if (tileSize === "16px") {
+        // 16px tiles - Top left tile
+        this._replaceTileXY(constX, constY, tileset.symbol, tileIndex);
+        // 16px tiles - Top right tile
+        this._rpn() //
+          .ref(tileIndex)
+          .int8(1)
+          .operator(".ADD")
+          .refSet(tileIndex)
+          .stop();
+        this._replaceTileXY(constX + 1, constY, tileset.symbol, tileIndex);
+        // 16px tiles - Bottom right tile
+        this._rpn() //
+          .ref(tileIndex)
+          .int8(tileset.width)
+          .operator(".ADD")
+          .refSet(tileIndex)
+          .stop();
+        this._replaceTileXY(constX + 1, constY + 1, tileset.symbol, tileIndex);
+        // 16px tiles - Bottom left tile
+        this._rpn() //
+          .ref(tileIndex)
+          .int8(1)
+          .operator(".SUB")
+          .refSet(tileIndex)
+          .stop();
+        this._replaceTileXY(constX, constY + 1, tileset.symbol, tileIndex);
+      } else {
+        // 8px tiles
+        this._replaceTileXY(constX, constY, tileset.symbol, tileIndex);
+      }
     } else {
-      this._replaceTileXY(x, y, tileset.symbol, tileIndex);
+      // Using RPN for X/Y values
+      const tileX = this._declareLocal("tile_x", 1, true);
+      const tileY = this._declareLocal("tile_y", 1, true);
+      const tileAddr = this._declareLocal("tile_addr", 1, true);
+
+      const localsLookup = this._performFetchOperations([
+        ...fetchOpsX,
+        ...fetchOpsY,
+        ...fetchOpsTile,
+      ]);
+      const rpn = this._rpn();
+      this._performValueRPN(rpn, rpnOpsX, localsLookup);
+      rpn.refSet(tileX);
+      this._performValueRPN(rpn, rpnOpsY, localsLookup);
+      rpn.refSet(tileY);
+      this._performValueRPN(rpn, rpnOpsTile, localsLookup);
+      rpn.refSet(tileIndex);
+      rpn.stop();
+
+      if (tileSize === "16px") {
+        // 16px tiles - Top left tile
+        this._getTileXY(tileAddr, tileX, tileY);
+        this._replaceTile(tileAddr, tileset.symbol, tileIndex, 1);
+        // 16px tiles - Top right tile
+        this._rpn() //
+          // Inc Tile X
+          .ref(tileX)
+          .int8(1)
+          .operator(".ADD")
+          .refSetVariable(tileX)
+          // Inc Tile Index
+          .ref(tileIndex)
+          .int8(1)
+          .operator(".ADD")
+          .refSet(tileIndex)
+          .stop();
+        this._getTileXY(tileAddr, tileX, tileY);
+        this._replaceTile(tileAddr, tileset.symbol, tileIndex, 1);
+        // 16px tiles - Bottom right tile
+        this._rpn() //
+          // Inc Tile Y
+          .ref(tileY)
+          .int8(1)
+          .operator(".ADD")
+          .refSetVariable(tileY)
+          // Inc Tile Index
+          .ref(tileIndex)
+          .int8(tileset.width)
+          .operator(".ADD")
+          .refSet(tileIndex)
+          .stop();
+        this._getTileXY(tileAddr, tileX, tileY);
+        this._replaceTile(tileAddr, tileset.symbol, tileIndex, 1);
+        // 16px tiles - Bottom left tile
+        this._rpn() //
+          // Inc Tile X
+          .ref(tileX)
+          .int8(1)
+          .operator(".SUB")
+          .refSetVariable(tileX)
+          // Inc Tile Index
+          .ref(tileIndex)
+          .int8(1)
+          .operator(".SUB")
+          .refSet(tileIndex)
+          .stop();
+        this._getTileXY(tileAddr, tileX, tileY);
+        this._replaceTile(tileAddr, tileset.symbol, tileIndex, 1);
+      } else {
+        // 8px tiles
+        this._getTileXY(tileAddr, tileX, tileY);
+        this._replaceTile(tileAddr, tileset.symbol, tileIndex, 1);
+      }
+
+      this.markLocalsUsed(tileIndex, tileAddr, tileX, tileY);
     }
   };
 
diff --git a/src/lib/events/eventReplaceTileXY.js b/src/lib/events/eventReplaceTileXY.js
index 0a5121687..ce8cce70f 100644
--- a/src/lib/events/eventReplaceTileXY.js
+++ b/src/lib/events/eventReplaceTileXY.js
@@ -21,21 +21,27 @@ const fields = [
         key: "x",
         label: l10n("FIELD_X"),
         description: l10n("FIELD_X_DESC"),
-        type: "number",
+        type: "value",
         min: 0,
         max: 255,
         width: "50%",
-        defaultValue: 0,
+        defaultValue: {
+          type: "number",
+          value: 0,
+        },
       },
       {
         key: "y",
         label: l10n("FIELD_Y"),
         description: l10n("FIELD_Y_DESC"),
-        type: "number",
+        type: "value",
         min: 0,
         max: 255,
         width: "50%",
-        defaultValue: 0,
+        defaultValue: {
+          type: "number",
+          value: 0,
+        },
       },
     ],
   },
diff --git a/src/lib/events/eventReplaceTileXYSequence.js b/src/lib/events/eventReplaceTileXYSequence.js
index c07466ac2..2fb605989 100644
--- a/src/lib/events/eventReplaceTileXYSequence.js
+++ b/src/lib/events/eventReplaceTileXYSequence.js
@@ -21,21 +21,27 @@ const fields = [
         key: "x",
         label: l10n("FIELD_X"),
         description: l10n("FIELD_X_DESC"),
-        type: "number",
+        type: "value",
         min: 0,
         max: 255,
         width: "50%",
-        defaultValue: 0,
+        defaultValue: {
+          type: "number",
+          value: 0,
+        },
       },
       {
         key: "y",
         label: l10n("FIELD_Y"),
         description: l10n("FIELD_Y_DESC"),
-        type: "number",
+        type: "value",
         min: 0,
         max: 255,
         width: "50%",
-        defaultValue: 0,
+        defaultValue: {
+          type: "number",
+          value: 0,
+        },
       },
     ],
   },
@@ -89,7 +95,7 @@ const fields = [
 
 const compile = (input, helpers) => {
   const {
-    replaceTileXYVariable,
+    replaceTileXYScriptValue,
     ifVariableCompare,
     ifVariableCompareScriptValue,
     variableInc,
@@ -145,11 +151,14 @@ const compile = (input, helpers) => {
     variableSetToScriptValue(input.variable, input.tileIndex);
   });
 
-  replaceTileXYVariable(
+  replaceTileXYScriptValue(
     input.x,
     input.y,
     input.tilesetId,
-    input.variable,
+    {
+      type: "variable",
+      value: input.variable,
+    },
     input.tileSize
   );
 
diff --git a/src/lib/project/migrateProject.ts b/src/lib/project/migrateProject.ts
index 25ddc077a..99aefb447 100644
--- a/src/lib/project/migrateProject.ts
+++ b/src/lib/project/migrateProject.ts
@@ -50,11 +50,12 @@ import {
   ValueOperatorType,
   isScriptValue,
 } from "shared/lib/scriptValue/types";
+import { ensureNumber } from "shared/types";
 
 const indexById = <T>(arr: T[]) => keyBy(arr, "id");
 
 export const LATEST_PROJECT_VERSION = "4.0.0";
-export const LATEST_PROJECT_MINOR_VERSION = "2";
+export const LATEST_PROJECT_MINOR_VERSION = "3";
 
 const ensureProjectAssetSync = (
   relativePath: string,
@@ -92,6 +93,22 @@ const generateMigrateMeta =
     };
   };
 
+const applyEventsMigration = (
+  data: ProjectData,
+  fn: (event: ScriptEvent) => ScriptEvent
+): ProjectData => {
+  return {
+    ...data,
+    scenes: mapScenesScript(data.scenes, fn),
+    customEvents: (data.customEvents || []).map((customEvent) => {
+      return {
+        ...customEvent,
+        script: mapScript(customEvent.script, fn),
+      };
+    }),
+  };
+};
+
 type ProjectDataV1 = Omit<ProjectData, "spriteSheets" | "scenes"> & {
   spriteSheets: (SpriteSheetData & { numFrames: number })[];
   scenes: (Omit<Scene, "actors"> & {
@@ -2473,17 +2490,35 @@ export const migrateFrom400r1To400r2Event = (
   return event;
 };
 
-const migrateFrom400r1To400r2Events = (data: ProjectData): ProjectData => {
-  return {
-    ...data,
-    scenes: mapScenesScript(data.scenes, migrateFrom400r1To400r2Event),
-    customEvents: (data.customEvents || []).map((customEvent) => {
-      return {
-        ...customEvent,
-        script: mapScript(customEvent.script, migrateFrom400r1To400r2Event),
-      };
-    }),
-  };
+/* Version 4.0.0 r3 updates EVENT_REPLACE_TILE_XY and EVENT_REPLACE_TILE_XY_SEQUENCE
+ * to use script values for X/Y coordinates
+ */
+export const migrateFrom400r2To400r3Event = (
+  event: ScriptEvent
+): ScriptEvent => {
+  const migrateMeta = generateMigrateMeta(event);
+
+  if (
+    event.args &&
+    (event.command === "EVENT_REPLACE_TILE_XY" ||
+      event.command === "EVENT_REPLACE_TILE_XY_SEQUENCE")
+  ) {
+    return migrateMeta({
+      ...event,
+      args: {
+        ...event.args,
+        x: {
+          type: "number",
+          value: ensureNumber(event.args.x, 0),
+        },
+        y: {
+          type: "number",
+          value: ensureNumber(event.args.y, 0),
+        },
+      },
+    });
+  }
+  return event;
 };
 
 const migrateProject = (
@@ -2680,9 +2715,13 @@ const migrateProject = (
 
   if (version === "4.0.0") {
     if (release === "1") {
-      data = migrateFrom400r1To400r2Events(data);
+      data = applyEventsMigration(data, migrateFrom400r1To400r2Event);
       release = "2";
     }
+    if (release === "2") {
+      data = applyEventsMigration(data, migrateFrom400r2To400r3Event);
+      release = "3";
+    }
   }
 
   if (process.env.NODE_ENV !== "production") {
diff --git a/test/migrate/migrate400releases.test.js b/test/migrate/migrate400releases.test.js
index 7bab8642a..506e5b3fd 100644
--- a/test/migrate/migrate400releases.test.js
+++ b/test/migrate/migrate400releases.test.js
@@ -1,4 +1,7 @@
-import { migrateFrom400r1To400r2Event } from "../../src/lib/project/migrateProject";
+import {
+  migrateFrom400r1To400r2Event,
+  migrateFrom400r2To400r3Event,
+} from "../../src/lib/project/migrateProject";
 import initElectronL10N from "../../src/lib/lang/initElectronL10N";
 
 beforeAll(async () => {
@@ -149,3 +152,112 @@ test("should keep Engine Field Update script values", () => {
     },
   });
 });
+
+test("should migrate x/y coordinate from replace tile event", () => {
+  const oldEvent = {
+    command: "EVENT_REPLACE_TILE_XY",
+    args: {
+      x: 14,
+      y: 7,
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      tileIndex: {
+        type: "number",
+        value: 1,
+      },
+    },
+  };
+  expect(migrateFrom400r2To400r3Event(oldEvent)).toMatchObject({
+    command: "EVENT_REPLACE_TILE_XY",
+    args: {
+      x: {
+        type: "number",
+        value: 14,
+      },
+      y: {
+        type: "number",
+        value: 7,
+      },
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      tileIndex: {
+        type: "number",
+        value: 1,
+      },
+    },
+  });
+});
+
+test("should migrate x/y coordinate from replace tile sequence event", () => {
+  const oldEvent = {
+    command: "EVENT_REPLACE_TILE_XY_SEQUENCE",
+    args: {
+      x: 4,
+      y: 11,
+      tileIndex: {
+        type: "number",
+        value: 0,
+      },
+      variable: "L2",
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      frames: {
+        type: "number",
+        value: 4,
+      },
+    },
+  };
+  expect(migrateFrom400r2To400r3Event(oldEvent)).toMatchObject({
+    command: "EVENT_REPLACE_TILE_XY_SEQUENCE",
+    args: {
+      x: {
+        type: "number",
+        value: 4,
+      },
+      y: {
+        type: "number",
+        value: 11,
+      },
+      tileIndex: {
+        type: "number",
+        value: 0,
+      },
+      variable: "L2",
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      frames: {
+        type: "number",
+        value: 4,
+      },
+    },
+  });
+});
+
+test("should migrate x/y coordinate values as 0 in replace tile event if invalid", () => {
+  const oldEvent = {
+    command: "EVENT_REPLACE_TILE_XY",
+    args: {
+      x: "",
+      y: undefined,
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      tileIndex: {
+        type: "number",
+        value: 1,
+      },
+    },
+  };
+  expect(migrateFrom400r2To400r3Event(oldEvent)).toMatchObject({
+    command: "EVENT_REPLACE_TILE_XY",
+    args: {
+      x: {
+        type: "number",
+        value: 0,
+      },
+      y: {
+        type: "number",
+        value: 0,
+      },
+      tilesetId: "d7042527-d20e-486d-93e6-66b9397df510",
+      tileIndex: {
+        type: "number",
+        value: 1,
+      },
+    },
+  });
+});