When using Fenix 8 and Index Sleep Monitor, sleep tracking stops once the watch is removed. The monitor keeps recording HR, but sleep/HRV data is missing. Looks like devices don’t hand off tracking. How to prioritize the sleep monitor?

I’ve been testing the Index Sleep Monitor together with my Fenix 8, and I keep running into a strange sync issue.

Night 1

• Went to bed with both devices on (watch + sleep monitor).

• Around 4 AM I removed the watch but kept the sleep monitor on.

• In the morning, sleep was only recorded until 4 AM. After that, no sleep data was saved, even though the sleep monitor was still on me.

Night 2

• This time I avoided wearing both devices at once.

• I had the watch on earlier in the evening, then before bed I removed it and put on the sleep monitor.

• The next morning, the report only showed ~10 minutes of data (from when I was still wearing the watch). The rest of the night with the sleep monitor on wasn’t counted.

It looks like if one device starts tracking sleep, removing it completely stops the recording, and the other device doesn’t take over.