Piglin trading farm set up: 

Place hopper in to chest, place carpet on top of hopper, place dropper on block behind hopper, place piglin on carpet on top of hopper, close in piglin so that he can't escape, place lever on dropper. 

Expected outcome: When lever flipped, dropper dispenses gold ingot, piglin picks up and inspects ingot, piglin then trades from loot table thus consuming gold ingot. 

Actual outcome: When lever flipped dropper dispenses gold ingot, piglin picks up gold ingot, inspects ingot then trades from loot table HOWEVER gold ingot not consumed. 

I have tested this on several different cells in a four piglin trading farm. Each pigln does the same thing. They trade the appropriate items from their loot table but they do not consume the ingot. Instead it goes into the hopper and then the chest. 

RE; Piglins not picking up gold:

I attempted the piglin farm set up using NavyNexus' most recent design however piglins would not pick up the gold ingot at all. I then went back to the design by FoxyNoTail (June 2020) because it still worked. This is the design I was putting together when I found the bug. I wanted to make sure it would work before completing the entire install so I tossed a lever on the dropper just to check. 

I'm not sure if it's a bug the piglins wouldn't pick up the gold in NavyNexus's build. It looks sound and I see no reason why they won't pick them up. I'll do some more experimenting with other options to see if it can be duplicated. If so, I'll create a new bug report for that issue. 

We have a server community and will do a work around for this bug where the gold ingots are filtered out and destroyed in lava in order to maintain the integrity of our duping rules.