My comments earlier about nickel plating didn't make the point that a copper undercoat or base is common with glossy, polished nickel finishes, which are typically electroplated in the older, more traditional style. (Old S&W revolvers are a good example...) I've seen plenty of those older type finishes degrade; I've seen few of the newer Electroless nickel finishes go bad.
Electroplating is an electrical process, with the nickel finish applied to a charged object. Electroless nickel plating is a chemical process with application through deposition. Of the two, the Electroless process apparently allows a more even, uniform coat, and makes for a harder, more durable finish. It doesn't require a base coat of copper to speed the process. The Electroless finish just isn't as "pretty."
I didn't think about that when I first replied, but the more-matte finish you often see in guns like the Bersa (and probably with my satin nickel CZ), and the Star Firestar and newer Star guns (they called it Starvel, I think) is generally the Electroless nickel finish, which is a different process, and doesn't require the copper foundation. Given this, the problem described -- as others have suggested -- is probably due to improper application. That also probably explains Bersa's willingness to make it right.
As I understand it, electroless nickel processing is a much more difficult process because of the harsh chemicals used and the related environmental protection issues. Waste disposal is complicated and expensive, and some places, it's just not allowed.
Anybody can pretty easily electroplate, using kits from Brownells or Midway, but electroless nickel finishing is a more technical and difficult process. Midway has a good "how to" video on electroplating on YouTube. I don't think that is practical with electroless nickel finishes...