XHA1 pinch roller fell off! What hold it in?

[Andy Wason]

A couple of years ago, my Xha1 tape mechanism stopped working (kept ejecting tapes). As I had a wedding within a few days, I wasn't able to get it fixed or spend the time to learn a new camera, so I bought a good used XhA1 at a fair price.
After watching an online youtube video of how to disassemble the drive mechanism. I got ambitious and decided to dissassemble the old XHa1 with the busted mechanism. As I took it apart, a rubber pinch roller fell out.
Not sure where it was supposed to go, I looked at the newer Xha1 that I had bought and saw where it fit in the mechanism. I tried to move it (the working one) with a pair of tweezers, and nothing seemed to be holding that one on either!
In my original busted XH I put the pinch roller back in the appropriate place and now the mechanism works!

I'm not sure if there's something supposed to hold the pinch roller in place, or whether it's just mechanically retained in position by the surrounding mechanism.

Anybody got any experience in this they'd care to share?
Thanks.
Andy