In 1.15.2, all vanilla and Quark flower pots have a missing bottom face due to a model bug which is fixed as of 1.16. The fix should apply to all vanilla pots, however any of Quark's pots that don't directly use the vanilla potted cross model will likely still suffer from the model bug, so this should probably be looked at either after Quark 1.16 drops or fixed before it in preparation. You can assign this one to me, shouldn't be too much of a hassle to fix.

I believe this will automatically fix when 1.16 happens as quark uses the same base model.

Nope, still affecting these seven in 1.16.4: