Hi I also have a white spot now appeared on my Vivoactive 3 and Garmin are telling me to go back to the shop I bought it from surely it is a Garmin warranty within the 2 year allowance? Watch is 18 months old...
Contact Garmin through their support website. I had the same thing happen last week. Mine is older, which meant that I had to pay for a replacement. Sad Face Day. However its cheaper than paying for a new one. You may be out of warranty at 18 months when it comes to the screen.