Interesting. I'd think that any issues involved would be in the bolt assembly and lever, since those affect the bolt locking up fully and also headspace. I've pulled several bolts and levers from mine and reassembled w/o problem.

Is it specific ammunition doing it? One brand/lot? Or anything you try? I've had some Federal that did that to me on a 99 in the past and other brands worked fine. It was odd.