Weird Upside Down Floating Entity Glitch (Fixed)

This issue was bizarre.

https://prnt.sc/ms0bfk (in case the image didn't work)

https://prnt.sc/ms0ax8 (in case the image didn't work)

https://prnt.sc/ms0cd9 (in case the image didn't work)

So I made a water world superflat world, and I went near a dungeon I had built, and the entities started acting up. They began moving strangely, and then started flying upside down, and some of them started losing body parts, and became strange upside down floating heads. Some started going inside each other and the models looked like some sort of bizarre mutant crossbreed. The terrain also occasionally disappeared momentarily, at which time a squid would almost always teleport onto my head. I have only had this in modded superflat test environment worlds (using my mod, and only my mod). Afterwards, Mcreator crashed, so I wasn't able to get an error log.

Edit: It has happened again, and it always happens at the same dungeon (a sort of ship covered in slime blocks that can be found in Oceans.)

And now the slime blocks have started floating too.

Edit: I think I have fixed it, actually. I don't know why it affected the things around it (e.g the landscape, other mods etc.) but it was a mob with a villager model that I gave a sword. I changed the mob and killed all instances of the broken version, and it started working.

Please can you close the ticket.