Something i noticed, is that if you have a stack of 2 fireworks, and another stack of three, you cant combine them in your inventory without dropping them, and then picking them up again. (dont know if that is intentional or not, and dont know if this is qualified as a bug)
Another thing I noticed about the inventory is that when you have only 1 open slot, you can only pick up items 1 at a time, even if they all fit into their own stacks. (again, dont know if this is intentional, and dont know if this is qualified as a bug)
Last point, when i was walking around the farm area for the mission, so objects would flicker in and out of existence depending on where you looked, and you could walk through them.
I was not doing any multiplayer, and i was on highest setting, with v sync (dont know if this is helpful)