I can't say for others but I've had issues with that gear breaking. Two different decks now the gear breaks and renders the machine useless. Apparently at one point Sony had a metal replacement available to authorized distributors but I've never even seen NOS pieces.
Edited: PALsite seems to describe the SL-F30 using a mechanism similar to yours pictured. Looks like that belt operates the loading mechanism and yes, again that arm gear assembly is known for losing teeth.
https://www.palsite.com/slf30tech.html