Sounds like you have a weight problem. Take your rig to a public scale (found at many truck stops) and have it weighed. Make sure it’s loaded with all the gear you would have for a long trip. Compair this to the rating found on the manufacturer’s tag...
in a tight turn going forward the top of the trailer will have a tendency to tip toward the cab of the truck due to torsional stress. And it appears that is what happened in this case.