I recently found a villager in r84 that traded 1 GroMeKi (or whatever it is, the bright green jam) for 1 emerald.

He also trades 2 emeralds for 4 GroMeKi Jam.

See the issue?

Infinite emeralds. I may have abused it just a little.

I don't think it's that big an issue because no one uses Villagers anyways.
But also, it's semi-rare for this trade combination to happen.

But yea, it's an issue still.

Maybe a possible solution for now is making this combination unable to appear with just one villager(if it works tho.... No idea how villagers work). That way you would at least have to find a second villager and that way it reduces the chance of the combination happening.