Used to have a .380 Guardian. It would jam if allowed to get dirty, but worked fine if clean. After a few hundred shots (the previous owner had something like 100 rounds through it, IIRC), the takedown button broke. Sent it back to NAA because I lost a tiny ball bearing when the button had popped out. They polished the chamber and feed ramp, and replaced the button. After the polish job, it needed to get a lot dirtier before it would jam. I don't know why they don't do that on all their Guardians. I then traded it for a Glock 23, after making sure it was reliable. A short time later, I got an e-mail from the new owner saying the darn button had broken again, and NAA was sending him a replacement, since he had the tools necessary for staking pins in place. I don't know if it broke a third time.
The takedown button broke in a way that didn't affect firing or anything; the slide was in no danger of flying off. But it did make it very frustrating to reassemble after field stripping, since you'd have to keep track of a button, a tiny spring, and a tiny ball bearing. Apparently that's a relatively common problem; there was a bad batch of buttons made a few years ago. They've probably got the problem ironed out by now, but older Guardians that haven't been fired much may still be suspect.