Sorry if this has been mentioned before, but I couldn't find anything and it bugs me, so here goes.

When holding an item (not a block or placable item) in your hand, the edges don't line up. That's about it. I'm pretty sure it started in 1.15.

To reproduce:

1. Take any item (again, not a block) and hold it in your hand.
2. It works best against bright blocks (I used sandstone in the screenshot).

Ignore the custom item, that's from a resource pack (which isn't the cause of this).