Bumping this as I'm still having this problem in Logic 10.3!! I can't work out the pattern as to what's causing it. It's usually after a save or core audio reset. If it happens to one plugin, it'll happen to at least 2-5/6. I've seen it happen to stock logic plugins, Slate, UAD, Fab filter.. It looks like there is no main offender to be honest, which points at a possible Logic gitch. This is making me start to look for the possibility of another DAW as it's becoming unworkable. If this happens during a client's mixing session, I can be chasing my tail for 30/40 minutes sorting it out, which just won't do.