For some time now I have been annoyed by finding incomplete or missing sleep data when I wake up in the morning. I finally found a solution to this, at least with the Charge 4. If your sleep data are incomplete in your app (e.g. it suddenly stops displaying data half-way through the night), you can click on the day in question under Sleep, touch the little drop-down menu in the upper right corner, and choose Edit Log. Then manually enter your actual wakeup time and Save.
I did this and suddenly the missing data appeared. The device had recorded it but, for some reason, wouldn't display it in the app. You can use the same trick if the app shows no data at all. Just create a new log with the time you fell asleep (if not sure, estimate it) and the time you woke up. The Fitbit app will then show whatever data is has for that time period.
I have done this with missing sleep data going back to last November and have managed to recover data for every night I thought I had missed. You can also do this on the web site, and more easily than you can with the app.
Hope this helps someone. It solved a major annoyance for me.
