I'm having the same problems as you.
I think, as far as locking "when it shouldn't" goes, it MIGHT have something to do with bluetooth, at least for me. Many times now, my watch has locked itself while on my body, and no amount of tightning the band, rebooting the watch, re-pairing it, and putting it back on my skin helps. At one point I got it to stop locking, but the moment I tried to move the watch on my wrist, it locked again. It wouldn't unlock until I turned on my bluetooth earbuds to listen to pandora on my phone while I worked out. Which seemed like a weird, unrelated event. But when I tilted my wrist to look at my watch, right as I turned on my headphones and they paired with my phone, it unlocked and stayed that way.
While on the elliptical, my watch was able to track my exercise for 25 of the 30 minutes I was going. But once my wrist got sweaty enough, and the watch started slipping around, it couldn't maintain contact with me and stopped tracking. It also locked itself again. It's still locked while on my wrist now.
I also cannot make my band go any tighter than it already is.