I used to work at a movie theater in high school. What you don’t see is that there is another platter below this one where the film winds back onto as it passes through the projector, so that it will be ready for the next showing.
One night a regular length movie (I forget which one) didn’t get set up properly, and didn’t feed onto the lower platter. The projectionist came in at the end of the movie to set it up for the next show and found the projector room filled waist deep with film. He was there until the next morning slowly spooling the movie back together.