The watch registers stand mode at how the gyroscope registers direction of your wrist. It's the easiest thing to do, and the easiest thing to do is to get a lazy ass. Just hanging your arm vertically and gently swaying it for a minute can claim the stand goal. Not really an "issue", just how the watch works.
I'll occasionally cheat the stand goal on road trips, because when I'm stuck in a truck for 5+ hours, I can't exactly get up and walk around. … That said, I've closed the exercise and move ring on road trips because the Alaska Highway is just that shitty in the winter … LOL.