That makes sense, Neil. It would also be interesting to see the tires on the trailer. If you pull or back a multi-axle trailer into a tight spot and leave it parked, the tire tread can permanently twist on the carcass. This can cause a strong sideways shake, that will flex things sideways even if they are blocked underneath.
This issue is so big that there are now reinforced evap and condensor cores in the Roof A/C units made for multiaxle 5th wheel trailers! Coleman lists them....higher price of course.
Back in late '89 my boss sent me to the Denver railhead to take pics and report on some damaged new LS400s. When I got out there, the railroad had sided the affected railcars and left the vehicles untouched. I confirmed the tiedowns, took pics of the exhaust systems lying under the cars, and was takng pics of the rear quarter panels when our 'rail guy' showed up.
"Somebody left the bolts loose?" he asked me. I didnt know, yet, who he was so I didnt answer. Once I started prying trunk lids open, he realzed this was not a manfacturing problem. The spare tires were standing up at an angle out of the trunk floor, the rear quarters were flared out like an old IMSA car, and everything underneath was hammered out to the outer skin of the quarter panels.
The cause was worn wheel flanges on the railcar trucks (the trucks start hunting, angling back and forth, and trying to walk the flange up the side of the rail....you watch them go by at railcrossings rocking like a drunken sailor). That lateral shaking is an ugly thing.
Couple years later I was at Cobo Hall with the SAE national meetings. I ran into a GM fellow I knew, and he told me about the days of shipping Vegas stacked semi-vertical (nose down, held up on framing). When Vegas got loaded in a railcar with worn flanges, they would find a little pile of metal about waist high at the end of the run to SoCal. The sideways shaking popped the cars loose, they fell on their nose, and the railcar hammered them down.
