I would not hesitate on it for 400.00. Those are the tightest production guns with the best parts out there. IF you had problems and you are not into tweaking them you could always send it to egw and for about 100.00 get their reliability package. You would have a great build gun, reliable at that point and still at an excellent price. I would say the same thing even at 500.00.
EGW made some of the parts on those and they would be an excellent place to send it.
If you look at the high quality parts sig used on those you could not even come close to them for 400.00
I was in the middle of something so let me come back and add this. The first problems sig had was caspian frame problems, but I thing yours is beyond that. The second problem was with the extractors which were made by EGW and they messed up on. It's rare as egw is excellent. I tend to think if you have problems it will most likely be the extractor. Of course there's exceptions to everything, but I would definitely check it IF you have problems. EGW has started making them better and more beefy and in fact George says if anyone has one of the ones they made that is acting up to contact him. Even if you have to buy one it's 25.00.
I think at 400.00 it's a steal.