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 the creepy building handyman falls onto the table-saw, it slices what appears to be his leg (or possibly arm) clean off. Except the saw-blade wasn't big enough to go right through his entire thigh (or upper arm for that matter), though... it only sticks up a few inches.
Answer: According to IMDb, the supervisor is basically chewing him out for being lazy and sleeping on the job, and then fires him.
TedStixon