Slide topper fabric wrinkles on one end

Could be the fabric isn't seated square. You can do what DSDPDon suggested and if that dosen't work try unrolling the fabric on the roller and slide forward or backwards. Just remember there is a lot of tension in the spring, use extreme caution and once you have it unrolled have a small screw driver available to place in the slot to keep it from releasing. Once you have it squared, slowing allow the extra fabric to rewind. I had to do this when I replaced a topper a couple of weeks ago. Probably would have been easier with two people, one on each end.

If the fabric is evenly spaced on the roller, DSDPDon advise is the way to go