(not yet working) movie box

thingiverse

This was a childhood dream of mine, and who better than my brother to share in it? He had envisioned a magical box containing endless 8mm movie cassettes, each one waiting to be played. Unfortunately, the box still remains a non-functional relic. The cassette fails to transport the movie smoothly, and I'm at a loss for how to fix it. Perhaps someone here has encountered this issue before and can offer some guidance?