Need help with celestar 8 mount please

[Altair]

Hi just recently i have a problem with the silver knob on the fork mount which controls slow motion. It has come loose. so much so that today when observing the sun it fell off....

Now i am hoping there is someone out their who has or has owned a celestar 8 wedge mount who may know what has happend? i am wondering if there should be a washer, nut or even a tiny screw which may have fallen off. Looking at it the sliver knob pushes onto the metal dowelling which turns the slow motion of the unpowered drive. i cannot see why it will not stay on. if anyone knows id be very grateful for an answer!

thanks

Dee