I had posted on this thread previously but, for whatever reason, the post isn't here.
Anyway, I suspect the handle is supposed to be silver soldered in place like the Winchester M70. Either the step was omitted or I'm just wrong (unlikely as that might sound!).
Regardless of whether the joint is intended to be silver soldered or not, the design is flawed. Knowing it is possible for the handle and base to come adrift (Winchesters do so often enough), the designer should have been aware of the potential for a serious mishap.
On the Winchester M70, if the joint should fail when a caertridge is being chambered, the bolt handle will go down but the rifle will not fire since the cocking cam, at least that portion of it which is milled into the bolt body, will not allow the striker to drop. On the Mossberg, if the handle is down, the striker can drop and fire the rifle although the locking lugs are not engaged. The only other rifle I can think of which has the same potential problem is the Browning A-Bolt. The bolt handle base on the A-Bolt is pinned though and less likely to fail.
This looks like a quality control issue to me but one which is more serious due to a design shortcoming. Regards, Bill.