I have personally, with my own eyes, seen three Bushmaster Carbon 15s break, two at the grip/extension tube junction, one at the front pivot. I have personally seen, with my own eyes, seen two Professional Ordnance (pre Bushmaster) Carbon 15s break, both at the grip/extension tube junction. I have personally, with my own eyes, seen two broken Plum Crazy and one Frontier lower. All of these at the same grip/extension tube junction. I have seen, with my own eyes, two broken CavArms lowers, both at the front pivot.
This does not even mention the numerous Carbon 15 uppers I have seen fail.
Like I said earlier, the CavArms at least made an effort to change dimensions in places where a weak point could be foreseen. They did negelct the front pivot point, but those I have seen, and the ones I have been told about, all broke from letting the upper fall unsupported.
Of the others, the majority of the failures I have seen in the grip/extension buffer area are from falling to prone drills, or from mortaring a Phase II malfunction. Either of these are normal, non abusive actions when done correctly.
Tell me some more how "supposed" these issue are.