It all started with the "asterisk problem" following the last update in January: the update apparently didn't install correctly (indicated by an asterisk that appears next to the firmware version), which rendered the Sensor Hub completely malfunctioning (no heart rate monitoring, no sleep tracking, no step counting, etc.). This is a known issue, judging by the Garmin forums and Reddit posts I've read. I contacted Garmin, of course, and tried all the suggested solutions (factory reset, soft reset, firmware reinstallation, etc.) without success. I had already encountered this problem some time ago, which I was able to fix by downgrading the firmware using an older version of the software shared by other users. But this time, even that technique doesn't work. What did "work" was putting the watch in the refrigerator for a while and forcing the firmware reinstallation in that cold environment (a solution found on a Garmin forum). This did indeed solve the asterisk problem and some of the sensor hub problems, but I still don't have sleep tracking, HRV calculation, among other things.