Back when I had the big extended length camper several years ago, which the rear jacks hung low on, I hit a series of large road cones with the right rear jack in a construction zone. It didn't tear the jack off, but it did tear the lower mount out of the plywood and damage it, plus bend the jack a little.
On the same camper, which was missing one of the roof vent covers, I had put a piece of plywood over the vent hole and a large rock on top of the plywood to keep the wind from blowing it off. Well, later on, I forgot about the plywood and the rock and I drove it down the road. When I got to where I was going, I remembered about it. I went on the roof to check it and both the rock and the plywood were gone. Hopefully someone behind me didn't get a large rock on their hood or through their windshield!
Again, on the same camper, I had put a bicycle inside the camper in the main hallway, leaning against the counter. The bicycle moved while I was driving and turned on the gas control for the stove. When I got to where I was going, I opened the camper door and was about knocked out by the gas smell. Fortunately, nothing lit on fire. I learned then to shut off the propane tank while driving.
Also on the same camper, when I was first bringing it home, I didn't have tie downs for it yet. I thought, I'm only going a short distance in town, I'll drive carefully and it will be fine. It was fine for most of the trip, until right before I to my neighborhood. Someone pulled out in front of me and I had to brake hard. The camper slammed forward and bent the front wall of the truck bed and dented the cab. Later on, I ended up having to unbolt the bed, lift it up and pull it back, remove the front bed wall, straighten it and then pound a pipe into the upper lip/channel, which was round and perfectly sized to fit a pipe into, to strengthen it, weld a piece of steel angle along the bottom where the bolts tore out, then put it all back together. I've never hauled a camper without tiedowns since then.