Multiline text to attribute

[Quasarrs]

Ezdxf=v1.3.5
I'm having problems with attributes and multi-line text again.
In the first step I create a block with multi-line text using your method.
Next, I want to change the value of the text in an already created document.
The software seems to change everything, but when viewing it nothing changes.

import ezdxf
from ezdxf.entities.insert import Insert

# STEP 1

doc = ezdxf.new(dxfversion="R2018")
block = doc.blocks.new(name="MY_BLOCK")

# Text, location and height not needed, because copied from MTEXT entity
attdef = block.add_attdef("TAG1")
# Define the multiline attribute as MTEXT entity
mtext = block.add_mtext("Default Value", dxfattribs={"char_height": 0.25})
mtext.set_location((0, 0))
# Set ATTDEF content from MTEXT entity
attdef.set_mtext(mtext)

attdef = block.add_attdef("TAG2", (0, -1))
# reuse existing MTEXT entity
mtext.text = "Another Default"
mtext.set_location((0, -1))
# Set ATTDEF content from MTEXT entity and destroy the MTEXT entity
attdef.embed_mtext(mtext)

# Usage of add_auto_attribs() with multiline ATTDEFs:
msp = doc.modelspace()
insert = msp.add_blockref("MY_BLOCK", insert=(5, 5))
attribs = {
	"TAG1": "TAG1-Line1\nTAG1-Line2",
	"TAG2": "TAG2-Line3\nTAG2-Line4",
}
insert.add_auto_attribs(attribs)
doc.saveas("block_with_multiline_attdef.dxf")


# STEP 2
doc = ezdxf.readfile("block_with_multiline_attdef.dxf")
msp = doc.modelspace()


insert_all = msp.query("INSERT")
for insert in insert_all:
    insert:Insert
    text_atr = insert.get_attrib_text("TAG1")
    print(f"OLD text: {text_atr}")

    text_new = "\\W0.8;NEW TEXT"
    atr = insert.get_attrib("TAG1")
    atr.dxf.text = text_new
    print(f"NEW text: {atr.plain_text()}")

doc.saveas("block_with_multiline_attdef.dxf")

Print -

OLD text: TAG1-Line1
NEW text: \W0.8;NEW TEXT

Open doc -