My Galaxy Watch SM-R800, purchased earlier this year has worked great so far. I've been using it to track hikes and exercise and noticed the altitude during my hike stayed at 260m over a 13k hike over variable terrain. I checked out the sensor in the "Test Mode" and it shows that it has failed. Everything else works perfectly.
Advice or instructions to seek warranty repair/replacement would be great.
Thank you for reaching out. I would be happy to assist you further. Can I please have your full model number and serial number/IMEI in a private message: http://bit.ly/2JH2rq2