Wildly inaccurate sleep data

[TCMII]

My Charge 5 is providing me what is obviously inaccurate sleep data.  After I wake up (usually between 3.5-4 hours) I usually do not get back to sleep but the FitBit says that I am still getting sleep at that time. This is not a case of "maybe you fell back asleep and didn't know it", I just lie there and the FitBit assumes I'm asleep.  This also happens when I lie down during the day. I NEVER fall asleep during the day yet it registers these sessions of simply lying in bed awake as sleep.  At this point I am prepared to return the unit, it is functionally useless for the only thing I purchased it for.

[RiekoC]

I believe Fitbits use movement - or rather lack of it, heart rate, and respiration rate to determine when you are sleeping. As best as I can tell, this seems to be true of just about all fitness trackers, not just Fitbit. Like you, if I wake up but stay in bed, my Charge 5 will show that time as still sleeping - usually light sleep stage. My Charge 5 will also show a sleep log after I've watched a movie, spend time reading, or anytime I spend sitting for extended periods. 

If what you need is a device to track your actual sleep periods, I think you would need one that tracks your brain waves - an EEG monitor.