Carryfast:
As I said animal seems to have followed the modern day ideas to the letter with obvious results.Unlike me in my time in which as I’ve said I didn’t differentiate coupling methods between steel or air.
In Animal’s example, it sounds to me that rough ground could well have been the issue, and possibly a lack of grease causing the jaws not to operate properly! 
So taking into account these freak occurrences, where one should keep an eye on ensuring the legs are both fully off the ground during the coupling, I’ll stick with lifting the trailer with the air suspension, and dropping trailers at standard ride height.
