While the battery of my Gear S3 Classic (SM-R770) last normally for 2.5 days, after the recent software update it decreased drastically for 12 hours.
Could it relate somehow to the (unwanted, but uninstallable) Bixby?
Agreed, same issue. Charge to 100% overnight, go to work, sometime an hr or two later I feel the watch getting warm, check it and it's 53%. Very sluggish response then, sometimes unable to use power off feature so often end up performing reset by holding button. Generally improves and behaves normally following reset, albeit at less capacity.
Same thing happens next day.