I’ve been having this issue for 6 months ever since buying an Apple Watch Series 9 in October. Never had the issue before. Watch is running 10.4 and my iPhone is a 12 Mini. I’ve done multiple resets including a full factory reset + setup as new (not from a backup). I’ve visited a “Genius” twice, talked to support by phone, reported the bug to Apple, and I even had the watch finally replaced in January. Nothing has fixed it. Rebooting the watch will fix it temporarily but it always comes back. I am at my wits end.