BuildCraft version: 7.99.15
Forge version: 14.23.1.2587
Link to crash report or log: https://pastebin.com/krNAAJFZ
Singleplayer or multiplayer: multiplayer
Steps to reproduce: After leaving on redstone engines for several days, chunkloaded the game crashes.
Additional information: Workaround is to remove said engines with the editor.

It has already happened twice with 7.99.14: https://pastebin.com/sByLqTk1

i suspect moving world might be messing with this? somehow there is no advancementmanager attached to the world

Unable to replicate, one of the other mods is definatly messing up the world