Hasn't worked for me. I started having this problem with with my S5 with watchOS 6.1.2. My watch sometimes gets stuck at 100%, sometimes doesn't (the charge, turn off trick seems to stop that), but it always turns off at a certain percent (right now, always at 66%; previously it was 48%). Attaching the charger boots it up, and it says it's at 66%. Use it for a min, and it shuts down again when it hits 66% again. When this first happened, Apple Support had me send my watch in to them in February to research the issue, and they sent me a new one. That new one shipped with 6.1.2, and I left it at 6.1.2 for a few weeks even after 6.1.3 was released. It worked fine. Then I upgraded to 6.1.3 and the issue came back again. I spent a couple weeks with a really good support guy, which ultimately ended up with me putting the 6.2 beta on it, so that I could send them in and they could downgrade it, in effect wiping it entirely including the firmware, from their own devices. They sent it back (same watch) with 6.1.3 and it worked perfectly again. I installed 6.2 myself, and it still worked, so I considered it fixed. I upgraded to 6.2.1, 6.2.5, 6.2.6, no problem, all worked fine. I installed 6.2.6 on June 1, and it WAS fine. But now three days ago - the problem came back again for no discernible reason. I've tried: unpairing/re-pairing; restoring from a backup; setting up as a new watch; completely wiping my iPhone and setting up as new, then pairing the watch; charing to 100%, turning off for 30 mins, charging up again; and probably other things I'm forgetting.