Your chamber problem with the NAA Guardian seems to be a fairly isolated one. We've had a great many Guardians through our shop by now and I've yet to run across one that exhibits the problems you've elicited. Frankly, were it mine, I'd send it back to NAA with a note to Ken Friel, their General Manager, politely explaining the problem and soliciting their assistance. NAA seems to bend over backwards to resolve QC issues; I'd be amazed if they didn't take care of your problem in record time.
AS for NAA coming out with Novak sights or something similar as an option, I suppose it's possible --- however, judging from the number of guns they're currently referring to us for this work, including some of their own, I don't see it as being a likely NAA option in the near future.