Aargh! Not another recoil spring assembly problem! I'm sorry to see you have this problem with your Shield .45. A couple of years ago a number of Shield 9 owners suffered defective RSAs. I know because I was one of them. My experience in trying to get a good replacement RSA was so absurd, it ultimately became amusing. The original RSA was bent, the first replacement was part of a rifle sling assembly (close enough, right?), the second replacement came apart just like yours, and I finally got a good one after 3 1/2 months. I chronicled my adventure in this thread:
Shield RSA one more time
Those events with the 9 did not sour me on Shields, because I am now the owner of a new Shield .45. So far (1500 rounds) the RSA is fine. I hope that S&W gets you a good RSA pronto.
Good Luck!