Why is sleep tracking data showing when not wearing device

Mine is doing this too, only got the last week, it is very annoying. It also demonstrates the watch isn't working properly, as when you're not wearing it there is no heart beat so it should know you're either not wearing it or dead, thus not sleeping

to activate sleep monitoring, the HR reading should be active at least as Garmin writes. I have the Forerunner 645 and sometimes Connect records sleep without wearing it and obviously without detecting any FC. the problem is Connect

Is Garmin going to fix this? This issue has only existed after an update a couple of weeks ago

As I'm not a Garmin employee, I don't know if they want to do something with it.

I hope so. I only noticed this after Christmas. Not a problem earlier in the year

It's the same with my Fenix 5. And this is something that started quite recently, like a couple of months ago (I have had the watch for almost two years).

Hey, my problem started somewhere around the beginning of december,that means my fenix 5x started to record only deep sleep when it is not worn, but the funny thing is that in november when watch was not worn during sleep time, there was no sleep data, so I also assume that this is software related. I don't understand why garmin mesures sleep when there is no hear beat to mesure when it is not worn. 

You guys/gals should be thankful Garmin Connect does not show that you are dead, when there is no heart beat detected, and stop complaining it just tells you slept deeply. It could be worse.

I suspect this is the classical "it is not a bug, it is a feature" case. Earlier people were often complaining the stats showed no sleep at all, when they did not wear the watch, so I guess Garmin decided to "fix" it in this rather unfortunate way. I bet it will change again in future, so I would wait a bit.

You could also perhaps try removing the predefined Bed and Wake Time, or setting them to the same value.

I have a Vivoactive 3 and as noted it started doing this recently for me as well.  I'm guessing it was added as a feature which in my case I'm happy with.  I wear mine for fitness tracking as well as part of a employer sponsored health program (Virgin Pulse) the program includes credit for sleep time of 7 or more hours.  Other fitness bands supported by the program are far more comfortable than the Vivoactive 3 to wear when sleeping.  After having it for several months I gave up wearing it during sleep because it is not comfortable and had to forgo the points earned.  As someone who almost always gets 7 hours of sleep this was regrettable.  As someone mentioned it seems to be taking habits into account to determine that you are likely to be sleeping and since it seems to still monitor movements during the sleep period I'm guessing it hasn't become any less accurate for those who choose to wear it.  Everyone has their own needs but they've made it more practical for me, I was starting to consider giving up on it and getting another watch.