Deliberate mistake: In the handyman's room, we see he has cameras secretly set up in the various apartments to spy on neighbors. But the placement of the camera spying on Mrs. Norris' dining room is kind-of ridiculous. It appears to be sitting out in the open on her dining room table. Sure, the handyman is a pervert, but there's no way he could get a camera onto such a spot without it being totally obvious.
Deliberate mistake: When Tree turns on the magnetic medical equipment, it's somehow strong enough to yank a big, heavy wheelchair up and pin Gregory in only a split-second, but not strong enough to instantly pull the screwdriver out of Tree's hand? Obviously this was done so Tree could have a cool moment where she lets go of the screwdriver and it impales Gregory... but it makes no real sense.