Had the same exact thing happen to our bedroom slide topper and it just kept getting worse. I used this video to remove the tension and remove the topper. You have to place a small screw driver or cotter pin into both ends to remove the tension. I had to remove the topper from the trailer but you might by lucky and not have to remove the topper. (If you do this, be careful and get a helper!)
https://support.lci1.com/videos/slid...ic-replacement
I found that there was never a screw on that side to hold the cord from sliding out. I added a #8x3/8 pan head screw to keep it secured Just follow how the other end is retained. The screw goes in the roller grove and compresses the cord. Hasn't been a problem since.