Villagers can't decide whether or not their trades are locked

Villagers can't decide whether or not their trades are locked, which causes the player to lose items and prevents them from trading.

Case 1. Background: I was doing regular trading when this issue occured. I had a farmer villager that traded 1 emerald for 5 pumpkins (original price 6). I put in 64 pumpkins and shift-clicked to claim the emeralds. The trade locked, villager took 30 pumpkins and I got 2 emeralds (should've gotten 6). I took out the remaining 34 pumpkins but only got 4 pumpkins and I also lost the 2 emeralds. Result: I got no emeralds but I lost 60 pumpkins (note: this may not have been the end result, it could have changed after I opened my inventory. In any case, I did lose pumpkins).

Note: This issue occured several times but I unfortunately filmed only one of the times and I stopped the recording after I closed the GUI. This description is based only on the one case where I filmed it so I don't know what happened next time I opened my inventory. It is possible that some of the items reappeared in my inventory as in Case 2, but it's for sure that I did lose items in the process.

Case 2. I also experienced a similar issue with the same villager when I was putting in pumpkins and carrots. The trade locked but I didn't get or lose any items. Next time I opened the GUI, the trade was unlocked and the same issue repeated over and over as I tried to trade with it. Result: Wasn't able to trade with villager in a while (seems like it started working again when I traded with the villager at night time).

These issues were experienced on a 1.14.2 vanilla server. I tentatively tried to recreate them in a test world but got no result. There are several factors that could affect this. I also loaded the world in 1.14.3-pre 1 singleplayer. At first the price of the pumpkins had changed to 7, but it soon went back down to 5. I didn't experience the two issues I made this bug report about though.

Image of the trading setup and video of the two issues: