First of all I'm not here to get support or to point fingers. I'm here because I have seen this crash reported a few times (66650, 66657, 66742, 66708, 66717, 66703) but none of them mentions which coremod is causing the crashes. I understand this forum is not the place to report mod problems (esp. coremod), but it might help someone else (maybe people stop reporting it more times).
Crashlog, Debug log
The mod causing this crash is NotEnoughIDs.
In the debug log this mod prints lines like this:
[18:14:20] [Server thread/INFO] [neid]: Patching class: "net.minecraft.world.chunk.ChunkPrimer" with Transformer Group: "TransformerGroupChunkPrimer"
[18:15:08] [Server thread/INFO] [neid]: Patching class: "ru.fewizz.neid.asm.Hooks" with Transformer Group: "TransformerGroupChunkPrimer"
Also I drop this notice from the mods curse page: "Worlds created with NEID is not compatible with clients without it."
Probably best to stay on 2760 for the time being. (I might start a new world without this mod, don't think I actually need it)