I've already exchanged this info with Jay, and it may or may not be related, but ...
my UC9, after close to 1000 rounds, has begun occasionally releasing the slide on it's own when I slap in a new mag. This happens with either mag I own, both a 10 and 13 rounder.
Maybe there's something weak about the slide lock?
My issue doesn't really bother me too much, as when it does this it always does successfully chamber a round, but I would rather it not.