Near the beginning when he is eating with the other old men he hands the plates of everyone near to him to the waitress. In the next shot everyone has plates in front of them again.
During Umberto's confrontation with his landlady after he returns with Flike, the position of the landlady changes between shots, so that a set of film posters appears behind her and her fiancée in the later shots.
In the kitchen of the landlady, when Umberto is chatting with the maid, she makes fire with a newspaper to get rid of the ants. After a few moments, we see that the newspaper is almost completely on fire, but in the next shot, less than half of the newspaper is on fire.