I was in nether and as soon as I had approached the Crimson Forest the game froze. I am sure this mod is the issue since when I took the mod out the game didn't freeze in the Crimson forest. The only different setting from the default ones was "Permanent Nether Weather" as ON. I have provided my minecraft install but the mod was disabled, I use CurseForge to manage my mods and resourcepacks. It includes the settings and crashlogs and everything else so you can replicate the issue. Just turn the mod on and go to the Crimson Forest and set "Permanent Nether Weather" as ON.

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I'm having the same issue on my end. At first, the game was only freezing. Then I finally got some errors in console regarding Java being out of memory, and today I finally got the crash-report!
There's something about a particle being created and... Well, you can read it yourself:
https://mclo.gs/i3pO44z

oh man so THATS the problem i was so confused as to what the whole "received passengers for unknown entity" thing was about that log is a lifesaver

ah yep there it is a while loop i forgot to delete thanks closing this