Andy:

I certainly agree that once the bolts become loose they will be seeing
shear load. I also agree that compressing the fiberglass shell over
time is a certain way for them to get loose. That sounds like a
pretty good theory. Of course, once they get loose, they'll be under
increased tension cycling too. As JJ has said, the key thing may be
to not let them get loose.

I can recall that my left rear latch had become a bit troublesome
prior to the failure. I now realize that meant that the bolt was
probably loosening in the left front.

My latest observation is that the hinge plate bolts on my trailer are
marked 8 8 which is not a high strength bolt. So I'm now thinking
that my corrective action will be to upgrade to high strength and
periodically monitor those bolts to keep them tight.

GW