Here's the temporary fix to the Gear S3 and Gear Sport battery drain issue
Something is rapidly draining the battery of my Gear S3 Frontier - Samsung Community
How to Prevent Battery from Draining on Samsung Gear Smart Watches - Appuals.com
So after I updated to the latest firmware I got extreme battery drain like from 100% to dead within an hour even after replacing the battery. HR sensor is dead wont turn