Similarly to in 1.14, Villagers' discounts (eg. 3 melons instead of 4 for farmer) will look like they have worked, but as soon as the game notices that you have accepted the trade (collected the items out of the villager menu), they change. It's really annoying that this bug is back even though 1.14.1 supposedly fixed it. Even still, it's back in 1.14.2