It happened to mine. I bought it new, always babied it on opening and it broke anyway. Wolverine exchanged the broken lower for a new one immediately. Once it breaks, there is no fix other than replacement that I know of.
I'm sure that stressing the hinge on opening will break it, but I'm also convinced mine broke because that plastic hinge absorbs all the return-to-battery forces. And it broke when I fired a shot at a coyote on a COLD December day.
So, to keep the new one from breaking I fabricated a return-to-battery lug, installed in on the bottom of the upper and glass bedded it into the lower. No more breakage, there is no more play between the upper and lower and it improved accuracy.
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