Other mistake: Sammy makes his film "Escape to Nowhere" with a Bolex 16mm camera. (I recognise it because I own one.) When he shows the film, we can see that it is on 8mm film.
Continuity mistake: After Boris grabs Sammy's cheeks, he runs and raises his left arm. Depending on the angle, his arm is raised or lowered.
Mitzi Fabelman: Everything happens for a reason.