Sporadically over the past month, my Fenix 7s stops tracking stress through the night. It varies from between midnight and around 2am. It tracks some nights no issues and then some nights it stops.
I can't remember what day it updated firmware, but a couple of days ago I updated to 20.12 (on Beta programme) hoping it would fix it. I don't know how to downgrade to last known official release to test this but since the upgrade, tracking has stopped consistently every night on 20.12.
HRV tracking is fine. If I remove the watch on wake up, and activate the sensor, it tracks again or I can reboot the watch to restore it.
I have done a soft reset but didn't make a difference. Am concerned it's a bug.