Certainly it's possible the casting composite is bad, but if it keeps happening in the same place and only since the new awning installation, I'd be suspicious of a faulty install alignment.
The photos of the break indicate a twisting force perhaps, or an improperly sized component. We've had unusual noises when our CareFree awning opens and closes, even after lubrication, but darned if I could find the source of any binding. Ultimately the aluminum awning roll end sleeve wore against the steel drive shaft, probably related to the telltale binding noises, letting the awning come open on the highway. My point is that these modern awnings with multiple arm components seem to be highly sensitive to even the slightest misalignment; I'm not sure an owner or even a certified service center is capable of spotting it.
I reckon the optimal thing is to have the manufacturer themselves examine the installation at their facility or perhaps at a large rally such as FMCA or Good Sam. If others can bolster your metal fatigue/casting composite failure theory by duplicating your experience, you are on the right track asking here. But also try casting your net on larger forums such as FMCA, iRV2, or RV.Net.
Joel
