Recently finalized a mob grinder and was taking a look at the drops when I noticed the items weren't stacking correctly. I hovered over the problem items and realized they had been assigned NBT tags. I checked the NBT tags of a few and saw they're all from Zenith.

It seems to be a low chance, as seen below there's only a couple problem items out of a few stacks. It's just mildly inconvenient and I thought I'd report it. The most-right items are the NBT items, the left are unremarkable.

All Zenith modules are enabled, and the mob spawners I'm using are modified through the spawner module. I'm not sure if these problem items have a chance to come from all enemies or if sometimes special Zenith mobs are spawning and they drop the items.