Some people will complain about the MIM trigger and hammer having 'soft cores,' but that's because they don't know that the 'forged' parts that MIM replaced were swaged/punched out of relatively soft flat stock and subsequently case hardened, not through hardened.
With that being said, I'm not aware if S&W's early MIM production had any teething issues. Even if it did, the flip side of the -5 having MIM hammers and triggers means that replacement parts are still in production.