At the projector, Rob's arms change positions between camera cuts.
When Jerry turns the lights back on at the end of the projected movie, Rob's projector is already off.
At the end, when Laura is sitting on the couch, her legs change position between camera cuts.
When Rob's film has finished, the lead-in reel on the projector is full while the take-up reel is empty (the opposite of what they should be after a film has been shown).