A problem common to all the units I have imported so far is stress fractures around the front side window adjacent to the entry door
Examination after removing the internal paneling reveals that it results in NO LOSS OF STRUCTURAL INTEGRITY.
I believe this is a simple design flaw caused by no side-to-side bracing / partitioning wall across the internals in the front section of the trailers. The amount of stress generated by the frame twisting around the doorway when travelling is the culprit. It causes the outer aluminum shell around the window frame to constantly flex, eventually resulting in stress fractures at the weakest points ... the corners of the window
It's an easy fix.