I am glad I am not alone. I have had my Gear Sport for 2 weeks with no issues, now all of a sudden it dies overnight. The last 2 night I have charged it to 100% before going to bed, now it is dead by morning. That battery drain is totally normal throughout the day, this is only happening at night.
My Gear Sport started doing this 2 nights ago too.
I backed it up...did a reset....and restored my settings.
THIS DID NOT WORK.
I went to bed it had 75% battery life and the watch died AGAIN around 4 AM.
I have not downloaded any new apps...still using the same ones from early this year .
Nothing strange for me since the factory reset. However I did not restore anything and did not install any apps or watch faces.
7% drain in the last ~6 hours.
During the day most have experienced regular battery drain, the problem seems to be draining overnight so it will be interesting to see what happens then.
I've been encountering the same issue. Always at night. I turned off a lot of things to check but nothing. I really think it was a software issue, but not necessarily firmware. I recall that a couple of the apps on the watch updated recently.