Hi. I have the same issue - what looks to be wear from rubbing on the back shell by the frame, on the streetside. Looks exactly like your photo as well as the one brownrecluse posted about back in 2013. He seemed to think it was an
axle issue. I also see that more recently brownrecluse was looking to get a new frame. My 1975
Boler is still all together with the dinette benches so I can't see the actual floor, but definitely can see from the underside that the streetside floor bows down significantly more than the curbside. The
axle seems pretty good, appears to have been replaced by the PO. Frame looks good but of course I dont know what I'd see if I lifted the shell. Is it your experience that this issue is often caused by the floor warp not the frame or
axle?