hmmm...sometimes if the camera is old, that upper roller gets seized up too--it'll glide easier on the regular rail, but it's still dragging--make sure that's rolling good. either that or you got a slight oversized metal bar. I used steel and aluminum no problems except the cut edges when they're not filed.
there should be an adjusting screw on the bottom and two on the sides of the railrider--the ones on the sides should be able to accomodate quite a bit of excess width--maybe you have to screw them back and PUSH the friction pads back in..they can get deformed and not want to go back in there. the top/bottom sometimes not enough clearance--that roller must be free to roll.