So a problem similar to many of the QD failures. On the QD, bolts are easy cheap insurance, I have upgraded them on my sled. Beyond that, the tools stay home, and I ride a fair amount. The belts themselves have been very reliable for me, except when you do not break in a '13 belt properly....
Both failures have the same result, a sled you are not riding out under its own power. I left my M7 with an expired DD in the woods for a couple of days and swapped it on the snow. Otherwise tow it out.
Too many parts needed to fix either failure. Just a belt is easy but I don't bother with a spare because those failures are extremely rare, just like broken chain cases. I just think the snowest QD failure hype is just that, hype. The system works, reliability is no reason to avoid it. If you are a modder, well maybe a chain case works better for you. Stock, I can feel a difference between my Pro and my buddies Assault. He couldn't believe I didn't go buy the same sled as his, I like the Pro better and the QD is part of the reason.
That was my chaincase failure, when I was in Wolf Creek. I consider it a freak accident, not an endemic problem. It appears the bolt sheared off in the driveshaft-- without backing out first (no marks on cover where bolt would go). The only reason I even found the issue was that my recoil broke, when I was in there to replace I noticed the chaincase. Rode the sled out--phew!