After nigh on two decades of RV life, I think the worst I've witnessed was an older tinkering enthusiast. As I was gaining on this older RV, something didn't quite sound right. I had to hurriedly swerve to avoid hitting the thing while it was about 3 or 4 feet in the air. (I was beginning to pass it.) After pulling over and talking with the couple I learned what they did. They took the small block v8 out and replaced it with a straight 6, added nitro for the hills and figured they'd tour the continent with better milage. Turns out they had a gutless time bomb. When I looked at the damage, what I saw was harrowing. The engine mounts failed along with the tranny mounts. The entire drive train dropped, bounced, compressed the drive line which in turn dove into the pavement, punctured the floor (leaving the content of the waste tanks all over the place) and consequently took the rear axel out as well.
On another note, I still wonder what the folks behind me thought when a sudden guest of wind pushed my RV hard enough to lift the right wheels of the ground. Nothing was damaged aside from the awning that was forcefully opened. I just got all 6 wheels down again, secured the awning and kept rolling.