i meet this bug likes "#4" at 1.20.1

What kind of recipes? It's always possible that a custom recipe implementation doesn't support remainder items and just consumes them.

likes this

Oh I see what's wrong. Empty buckets are being considered water buckets for some reason and as such get consumed.

I just tested that recipe in a test modpack using a vanilla crafting table and it seemed to work properly. Maybe there's a mod conflict?

The actual issue was that shapeless recipes weren't properly checking the fluid contents of the buckets.