Crashing every few minutes and quest complete notification spam

[snydej]

I'm playing Forever Stranded and just completed the "Killing" Quest". Now I am getting repeated notifications that the quest is complete. As soon as the last one fades out another one pops up. Restarting Minecraft has no effect and since this started Minecraft will only run for few minutes before crashing.

After this most recent crash I lost both the ability to see what quest rewards are associated with this quest and the ability to claim the rewards. I can still see the requirements on the right side but nothing is shown on the left side below the quest description. The icon for the quest had a green background as though I had claimed the rewards, even though I never did. At this point I tried reseting the quest using /bq_admin reset 29. This didn't stop the quest complete spam and it still looks like there are no quest rewards though it did reset the quest progress. Finally restarting Minecraft after this seems to have stopped the notifications but the quest rewards are still missing. After this I tried the "Quest an Loot reward update" quest which runs these 2 commands: /bq_admin default load and /bqs_loot default load. That finally fixed the quest rewards. Then I tried /bq_admin complete 29 to see if the quest might work this time but the spam started again.

I am using:
Better Questing 3.3.237
Forge 12.18.3.2511
Minecraft 1.10.2

Here is the latest crash report:
https://gist.github.com/snydej/c86d816f2b488217bc5799368a3c772f

The complete log is here:
https://gist.github.com/snydej/3096c091417d192ee9c6fcd702dc0afb