Zombified Piglins are messed up

I have a zombie pigmen farm and the pigmen act weird. There drop system is very weird, sometimes it works totally normal and other times I can kill twenty pigmen in a row and I get nothing. On top of this the pigmen despawn in a very short amount of time where previously they would never despawn until I killed them. And how often they spawn is weird to sometimes, they will keep on coming and then sometimes minutes go by between a pigmen spawning. Can you fix this