I have an identical issue. I got a new RAMI, fired 500 light target cartridges with no issues, but when I disassembled the gun, I saw the peening - much worse than yours, though. I called CZ, and sent them pictures depicting the problem. The gun is not safe to fire, and I will be sending it to CZ for repair under the warranty.
This peening problem has never happened to any other guns I have, and this is completely unacceptable. It is sad that CZ manufactures RAMI with such a bad quality.
By way of speculation, I know that RAMI comes with "white" metal barrels, and our barrels are of "black / dark" metal. Maybe "white" metal barrels do not have the same issue... Maybe they are stronger... Regardless, the quality is bad.