When Larry knocks to borrow the $10, there is a chair blocking the door but when Jack opens the door the chair is beside the door without Jack moving it.
After Max tells Larry, "Tell your friend I'm gonna kill him" and leaves, Larry immediately conveys the message in such a way that Max would have clearly heard him.
It's never explained how Jack is able to leave the apartment to get to the funeral home with Max keeping constant watch.
When Max comes out of the kitchen and Janet tries to block him, you can see the placement of the wall not aligned so you see the back of the set.
When Jack opens the door for Larry there is just a blank wall outside the apartment. The scenery is gone.