the problem arises from the thing not being dirty enough. You're spoda throw it into a puddle and drive over it a few times before shooting it!
I am, of course, kidding, and thusly will post all the required smilies to emphasize such:
sounds like the recoil rod assembly spring which I'm sure you're going to check out and get squared away. I, as well, have a shiny new G17, but ain't had no problems widdit.
good luck and good Glockin'!