Out of curiosity, how did they fail? I have one of their slings and I like it, though I admit I haven't used it a lot. So far the only problem I've ran into is that the webbing can get twisted inside the adjustment buckles but I couldn't tell you how that happens because I haven't done it, other people have done it to my sling when playing with it. I'm also a bit worried that the quick release might be to easy to release if you snag your gear on something, but so far no problems.
Personal Observation from a LMS Defense class:
Two Magpul MS2 slings came apart resulting in carbines falling to the deck. In both cases, the strap that loops through the D-ring and then back through the tri-glide buckle, loosened itself out of the the buckle (see attached pic). At the very least, users need to be aware that the strap's end needs to be looped back through the buckle one more time or the strap's end needs to be taped in place.
Personal Observation from a Stone Cobra Tactical Carbine 1 & 2 class:
Same as above.