I have an 24 ft round above ground pool. I have a solar cover reel, which I love, except for one thing...The little black nylon screws that attach the straps to the cover continually pop out when I roll up the cover. It always happens in the middle straps never on the end ones. I have adjusted the tension and uniformity several times to no avail. Has anyone else had this problem....and more importantly has anyone come up with a solution? Thank you so much in advance for any helpful guidance!