https://gist.github.com/Vyraal1/226618ad0a7adb0f0e52199097750513

This is in a pack-dev environment for FTB Interactions, was checking worldgen in a nearby swamp and used Worldstripper to check oregen, deleteing some water blocks. Not sure if any of those are related.

I'm not sure what could be causing this, but iterating through the entity list in a different way should solve this.

1.12.2-2.4.0.5 probably fixes this.