It looks like YO and I were both commenting at the same time to the
effect that it is more likely a tension failure. However I don't
agree that the gas spring force has much to do with it. The gas
spring force is small compared to the strength of two 5/16 cap
screws. I suspect it has more to do with the inertia of the lid in
longitude with some combination of vibration and road bumping creating
the load. Heaven knows my trailer has seen some bumpy roads.

GW