MY 637 showed the same peeling under the grip that the OP described. I called Smith & Wesson and the service rep laid the blame on the cleaning solvent I was using - Hoppes #9. Nothing in the owner's manual about which solvents to use or not use. Anyway, I sent the gun back to Smith and they replaced the frame instead of recoating. No reason was given as to why they did that. Turnaround on the fix was 2 weeks or so.