10-07-2016 07:43
10-07-2016 07:43
10-16-2016 07:16
10-16-2016 07:16
@Juldap Welcome to the Fitbit Community! Autodetection is based on your movement. When you haven't moved in over an hour, algorithms assume that sleep has begun. Morning movement tells your tracker that you're awake. If you're not moving but not asleep for long periods of time it's possible for your tracker to falsely record sleep, in which case you can delete the sleep record from your dashboard.
Also, check the sleep settings to check which setting works better for you. For the moment, delete the false sleep log and log it again manually, you can do this on the sleep tile on the Fitbit app.
Let me know how it goes!