To replicate the issue is quite simple: you just need to break an armor stand; Once you do that, the game will crash half a second later. The issue seems to be related with the armor stand's dropped item and something else on the mod, since I need to remove Accessories mod from the mods folder to be able to join the world and pick up the dropped armor stands.

Minecraft 1.20.1 Heavily modded
Fabric

Initial crash log: crash-2025-03-25_17.40.29-server.txt

This crash seems to be caused by just-like-rays. Does disabling the mod mitigate the issue?

Update The Aether to beta 7

Huh, weird. I remember updating Aether to Beta 7 and this error still happening. But now I tested again and nothing happened. Thanks!

I'm sorry, I posted the wrong crash log
Here's the ACTUAL crash log: crash-2025-03-25_17.22.01-server.txt