After transforming back to a player from a modded creature (Mosquito from Erebus mod), it seems like the transformation was left in the world as a hostile mob.

I could not sleep at all, (transformed near bed so blocked by monsters). Peaceful difficulty did not fix it. Placing mod things like bees that should kill all hostile mobs in the area did not fix it. Logging out while the area was chunkloaded did not fix it. Leave the area completely did not fix it.

I restarted the server after changing the difficulty back. Had a hostile Mosquito completely immune to damage where I transformed. Kill all entities did not kill it. Leaving the area despawned it though.

I do not know if this is an Erebus Issue or a Metamorph issue or perhaps even a Waystone issue (I might have teleported back using one and then transformed to player)

DarkPacks/Crackpack-3#116

I don't really think the issue is on my end, but I guess Metamorph is triggering some rare condition with those mosquito mobs which causes this bug.