Well I think I have the fix to the missing and backing out screw problem on the rear cap. I have had 2 of them with this issue for a while. I have only moved twice with it and traveled 7-8 hours on the fix. But so far so good!! I got a bag of the factory screws with the painted heads. Went to Wally World and bought Hillman plastic anchors, 591296 - #4-6. I started the new screw into the anchor and then pushed it past the outside rail to the top of the overlapping panel and then tightened it up.
I hope this works for you also.
Safe travels.