crash-2023-11-04_04.49.40-server.txt
I crashed while fighting a magma slime.
Upon trying to reload I got an "invalid player data" error, I had to remove my cosarmor player data to resolve it. After returning to the overworld & saving I was able to re-add the cosmetic armor saves & suffered no loss.

It seems to be really rare as I wasn't able to replicate it, but I suspect maybe it had something to do with the curios I was wearing from Artifacts (invisibility cloak & I think the yellow terraria fist) since that was the only new thing I recall adding to my setup around that time the armor I was using in the cosmetic slots were the wolf head from enemy expansion, the body & legs of the end armor from monsters & mushrooms, & vanilla chainmail feet.

The crash has nothing to do with this mod. And...
CosmeticArmorReworked should only complain about "Failed to load CosmeticArmor data", it will not stop a player from playing the game if CosmeticArmor data got corrupted.
Normal player data corruption caused by a crash is beyond this mod's reach.

The weird thing is that it was resolved by removing the cosmetic armor data from the folder starting the world & I was able to re-add the cosmetic armor after saving when I entered the overworld. So whether it was caused by something else or not it still wouldn't load until the cosmetic armor save file was temporarily removed & I re-added the cosmetic armor save later & suffered no loss of items.

It is a rare issue & I haven't run into it again despite fighting more magma slimes with the same weapons & equipment (& cosmetic armors, though I didn't use the same curios), but it seems to be linked to the mod somehow. If it was data corruption, I don't understand how I have all my items still after re-adding it when I saved in the overworld.

If I had to make a guess, I would say maybe the mod doesn't play nice with the invisibility cloak from Artifacts? it was the only thing I think I wore differently on the first nether trip.

Hmm, it might not be a problem with player data then.
The crash might be caused by some AI modifying mod didn't play nice with mod 'Dimensional Threading Reforged'.
If you encounter the issue again, please share the log when you can't start the world.

I think this log might be from when it happened, apologies if I am wasting your time.
2023-11-04-4.log
I think I ended up disabling Dimensional Threading Reforged a while ago so if it was that mod that sounds plausible though I have no clue why that would have a bad reaction with ai which in turn caused my cosmetic armor to crash the game till I left the nether.

It is just a very weird bug altogether, I will probably see if Dimensional threading has a github and notify them too.

The log shows TerraBlender failed to load it's biomes for nether due to broken level.dat.
I'm sorry, I have no clues.