villagers can't restock

after selling maximum items villager can take he will not restock

how to reproduce

1.get an villager (for me it was an farmer
2. get him up to lv 3
3.sell melons as much as you can to him
4.wait a couple of minutes
5. after he restocks at higher ammount of items for emerald sell more melons to him

Observed results
Villager will never restock
Expected results
Villager will restock