Venu 3s goes automatically into sleep mode during the day while I'm being active. Sl

I've been having trouble with my Venu 3s sleep tracking for a few weeks now.

I have a sleep schedule set. Last week my 3s wrongly recorded me sleeping for over 22h, well beyond my 7h sleep schedule,  i even had 16k steps during that time. 

Today I looked at my watch, an hour ago (1pm) and it shows the dnd and sleep mode is on, while my sleep schedule definitely hasn't been set for this time. I toggled it off. Looked at my sleep data from last night, which at first recorded almost 8h of sleep, but now shows no sleep data anymore..... 

Even more annoying, in the last hour, I keep having to toggle sleep mode off as it automatically springs into sleep mode again. Already did a restart of the watch. 

In the last few weeks I've also had the trouble that a 1.5h nap deleted a 6.5h sleep from the night before.

Why can't Garmin get sleep tracking right? I don't even care about the sleep stages, because no watch can get this truly right. But a €500 watch shouldn't see me as asleep for almost a full day while at the same time logging 16k steps. What does it think, that I'm sleep walking?....

And why does it keep going into sleep mode while I'm being active?

It's ridiculous and I'm this close to returning the watch and going back to my Venu 2s.