Villager trade item duplication

In villager trades if you place an item or two for trade and then try to move a full stack of the same item to the trade the items occasionally duplicate or become 2 full stacks of 64 items.

Ex. Have just over 64 items ( like 68) add 3 items from the small stack and than try to move all the 64 items into the same trade. You'd occasionally end up with multiple stacks of the item somehow.