I have a villager crop farm where a farmer would farm and then throw the crops to another villager and recently I have seen a few behaviour where:

+(When farming potatoes)the farmers would get stuck in a loop near(1-3 blocks)the collecting villager throwing the crop(not get picked up from hoppers hopper minecarts or any other means) and then picking it up in repeat rapidly 

+In a full one water block radius of farmland there would always be one block in one corner where the villager would not plant or collect crop

+Sometimes farmers would stop stand in place trying to get to a full grown crop