The sensor cover has repeatedly come off. I really liked the watch but this is a sign of poor quality. Having read several posts from others having the same problem, I believe this is a known issue. I hope it can be resolved.
I've seen several posts about the rear sensor cover coming off on the Galaxy watches, but none on the Active 2, at least in my limited perusal of the forum. Have you had it in hot environments, like sauna, hot tub, hot shower?
Never. I switched from a regular watch so out of habit I don't wear it in the shower or anywhere it could get really wet. It is supposed to be waterproof, so I did wear it when washing my hands, etc.
So far I have been able to put it back and everything works but I am sure that won't continue.
It is clearly a design issue. The sensor cover is held on solely with glue, it will work for some time but will inevitably fail. I really like the watch but there are other options on the market.