So the screw acts as a key in the channel, stopping the lens from rotating as it telescopes. If the screw is too long or wide, it will jam in the channel instead of sliding. Usually those key screws have a cylindrical end where they slide in a channel, and the thread up near the head. Its possible someone replaced it with the wrong screw.
Since there is an external screw hole that goes through the S mount casing, I don't see how anything could "slide" up