Here is a crash log of the issue.
https://gist.github.com/thakyZ/6d1a30bcae577451f02321f889f2c3ba
I had a crash in 1.20.1 ("All the Mods 9 - To The Sky" Mod Pack v1.0.5) when opening the Little Tiles little bag, seems to be some kind of screen rendering bug, but I am unsure as to how to fix it.

The steps to reproduce:

1. Open little tiles bag.
2. Chance to crash, not 100% of the time. (Seems to be an edge case)

I will be reporting this to JEI as well, and will link this issue on their repo and their issue here in a moment.

JEI Issue: mezz/JustEnoughItems#3561

Never mind, I figured out it is another mod all together. It is in fact Modern Fix. Disabling the one of the options (I'd still have to do some more testing) fixes it.