Amount of cake differs between shots, when Vincent feeds his mother.
Discontinuity is apparent between the shots when woman is throwing the trash. She is first shown crumpling the bag, but in the next shot, bag is not crumpled.
When on the roof, we see inspector looking at the girl, but in the following shot he is looking away.
Discontinuity is apparent in the morgue scene, when woman enters. Positions of people clearly indicate another take.
Discontinuity apparent between shots when Vincent is wiping his mother's mouth.
When killer is finally revealed, we can hear him speak, but his lips don't move.