I've never had trouble with mine (had to satisfy BC) however it definately sounds as though something is amiss. I suggest you take it to an Authorized Dealer and have them check it out to see if the threads are stripped, perhaps they weren't cut properly in the first place.
I think the best way to tell would be to take the limb assembly off, then, without a limb pocket (for lack of a better term) run a bolt down the threads to see if it wobbles more than normal. This should tell if the threads are tight or not.
I would also check the bolt/bolts for any burrs that may have caused the problem. After all, a grade 8 bolt would quickly cut its way through 6061 T6 aluminum.