The texture is not visible in the hot bar or in the inventory.
type=item
items=rotten_flesh
nbt.CustomModelData=3

Please provide your latest.log

Issue can be reopened when logs are provided.

The texture is not visible in the hot bar or in the inventory.

I had the exact same issue as you and I was able to solve it by removing the eating-animation-1.21+1.9.72 mod. Do you happen to have the same mod installed, considering that the affected item is rotten flesh? Have you noticed if this happens with food items, or mob loot, or any other recognizable pattern?

If you're unsure of what mod might be causing this, I recommend that you remove half of your mods at a time to narrow it down and find out which mod might be the culprit.

I had the exact same issue as you and I was able to solve it by removing the eating-animation-1.21+1.9.72 mod.

Known issue #418

Known issue #418

I'm glad to see that we're not the only ones experiencing this, thank you for letting us know!