Thanks for suggestion, but access to the depth adjuster knob resticted and
is very difficult. Secondly I'm not sure a machine nut would be any better
strength-wise to absorb impact shock of nail gun.

What I'm wondering is whether other users of this gun have a continuing
problem with this or is this a one-time rare event, just like the "rare
event" of the bad spark plug I had.

IF this happens again and again, I'd just as soon cut my losses and move
onto a different gun?

Cheers,
Jim

I don't have that gun, so the best I can do is offer some sort of
vague advice in the form of:
perhaps you could repair the knob by reaming it out and epoxying in a
threaded insert... or maybe just replace it with a machine nut...