Yep.
Just happened to mine the other day. I can't say that I noticed anything missing, but I have the same problem. 1100rds through and about 250rds with the Galloway 22#
I've also noticed that because the spring has been hammering on the takedown plate, the plate has started hammering on the frame and started mushrooming the polymer.
I've found that I can get it back in place if I smack it a couple times, but, well, that is less than ideal.
I haven't contacted S&W yet because, well, it's my only carry weapon.
Also happened to this guy
He just got his back this week, was without for 51 days