I have a Samsung Gear Sport watch which is approx 6 months old. In the last week it has started to discharge overnight. Normally I could get 2.5 days use between charges. Last night it was on 87% after being fully charged in the morning, this morning when I woke the watch was powered off and when I started the battery was at 0%. The watch was working fine over the weekend.
I have deleted any new Apps etc which was only two new watch faces. This morning I have done a full reset of the watch and declined updates to see how that goes. Are there any Samsung Sport users here and are you experiencing similar issues.