that's a really interesting observation. Also, I would want to make sure that the lower head lug is held without any slop. If there is slop there, that would also magnify the loading. The setup looks suspiciously slapdash to me.

I had an unexpected failure on a fatigue test once that turned out to be due to loose bolts. It turns out that this has been studied. It results in impact loading, which accelerates fatigue crack initiation and growth by a significant factor. I need to research it again, because the subject keeps coming up.