Villager discounts shown but not applied

So I created a artificial village for a village hall, I have good reputation so I have heavy discounts. When I look in the trade gui, it shows the red line and says what the discount is, but when I trade the items in stacks it takes the items for a discount then the numbers update to less as if there was no discount applied. If I try to trade the exact amount for the discount, the trade won't go though as if I didn't have enough but the xp bar goes up. After closing the gui the xp bar is set to the exact as it was when I first opened the trade gui.