Hi there @davidnicholas59.
Thanks for the detailed information shared and for all the troubleshooting that you have tried so far. I understand where your concern is coming from. As you may know Fitbit estimates your sleep stages using a combination of your movement and heart-rate patterns while you are sleeping. Several factors can affect heart rate, including air temperature, stress level, alcohol or caffeine intake, immune response to illness, and medication use
Spikes in your heart rate during sleep may be caused by sudden movements (for example, waking up and getting out of bed), or a weak signal due to wrist placement. To get more information about heart rate Review our tips in How do I improve the accuracy of a heart-rate reading?
Additionally, I'd recommend trying the following steps to make sure your heart rate is working:
Switch the Heart Rate settings from On to Off and manually sync your watch. To switch the heart rate settings on your watch, from the main screen of your watch, swipe left until you see "Settings", next swipe up until you see "Heart Rate" and switch it to Off.
Once it's done, manually sync your Ionic. To do so, open the Fitbit app, and pull down the screen
Next, switch it from Off to On and manually sync your watch once again.
Confirm that your tracker is snug on your wrist (the lights shouldn't be visible)
Make sure you are not using the begin sleep now opting in the Fitbit app.
On a side note, I've moved your post to the Ionic board to keep our forums organized.
Hope this helps.
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