Continuity mistake: In the flashback scene where Dustin Hoffman is in the hotel bathroom on the floor, he puts a coffee mug on the toilet, then the view switches and when it comes back the mug is gone, never to be seen again.
Continuity mistake: In the flashback at the hotel room, as the woman is laying on the bed, one of the straps on her dress falls off. A second later it's back on.
Continuity mistake: In Act I, Dustin Hoffman pours a glass of milk and then carries it to the window. The level in the glass varies depending on whether we see a close-up or a medium shot.