Both Heart Rate and Pulse Ox quit working today. No red or green lights on the back sensor. Software says "stay still" and otherwise seems to be expecting sensor inputs that are not present. Did multiple resets.
Chatted with support today. Further examination it seems to be a mechanical failure. The round plastic sensor with the red and green LEDs on the back is separating from the case. The watch was a 7x24 wear for exactly one week short of 5 years. Not abused but lots of miles hiking and cycling.
Garmin doesn't have my model for exchange and offered me a different F6, which won't match my titanium band for $230 or 20% off list price for a more modern F7 or F8. Not sure which way I will go.