Same issue and not knowing how long this learning is going to take is not acceptable, particularly when it drives support calls from relatives wondering what is going on. Watch was updated about 4 days ago. Turning off the Optimized Battery charge setting will allow the watch to go back to its full charging previous to the WatchOS 10 upgrade. There are numerous threads on this upgrade issue and what happens in the real world is people keep leaving their watch on the charger thinking it is not done charging at 80% when in reality this new WatchOS10 has changed how it behaves without letting the consumer know. :-(