Did you ever get an answer on this? I’ve had the exact same thing and it’s very annoying. It was fine before the stupid REM update! There are days it will show the correct hours of sleep then randomly through the day it will add a blank mark and remove hours of sleep. What is the deal Garmin??
Same issue here. And, you can no longer edit sleep data for any day before the current day on either mobile or web now. This is a terrible change. It says I woke up at 4:30 AM on Friday, but I didn't get up until 6 AM. I just discovered this and was going to correct my wake time, but the option has been removed. Terrible update. This needs to be fixed.