I fixed this on one Roleiflex by adding a washer below each side panel attachment screw to the front of the camera. 2 total? You might have noticed a brass washer or two already in there. These washers are thin- .004-.008 inch (.2-4mm).
I think that the panel can get bumped and bent just enough to bind things up. Look at the panel when removed to see if there are any bends or dents- very slight.
Of course, best to send it to someone who really knows what is going on. I am just bumbling around and found this to work on one Roleiflex. A real repairman would have seen this many times and would know the best fix.