Low hr activity

I'm normally running with my chest strapon... yesterday I was pretty surprised about my unusal low HR and found out that th chest strap ran out of battery. I'm running 4 times a week and have a pretty good idea what my HR normally is, the watch shows at least 20 bpm less than the strap. Pretty annoying!

Updated 11.00 still the same....

Was good on10.00 now on 11 again

I received a new device from Garmin Support - same with low HR during activity (80-90 instead of 150-160). The only "solution" I found is to stop activity, start different one, wait for reliable HR, stop it and start the right one - it takes ca. 15 minutes.
I suspect this is a problem not with particular device - it seems like for some reason Fenix 5s doesn't work on some wrists (skin color, hairs, size of wrist). I'm pretty sure my defective Fenix 5s would work on someone's else wrist well.

I have problems with walking activity. The others work. Created own walk activity and i works good

Huh, went back and looked at some older activities. Looks like hiking always seems to work, but walks do not. I have 2 out of 3 walks are correct, but one is really bad with my heart rate going down as I climbed a 200ft incline over 1/4 mile. Last I checked, I wasn't super-human. So it seems the walk activity has issues. Or... anything that generates a VO2 max result. Perhaps the CPU is getting too taxed on some calculations and it cannot keep up with the sensor. It isn't like these CPUs are speed demons.
Garmin, you may wish to look into the legitimacy of these complaints. It may not be the sensor code, but something else bogging the device down.

Huh, went back and looked at some older activities. Looks like hiking always seems to work, but walks do not. I have 2 out of 3 walks are correct, but one is really bad with my heart rate going down as I climbed a 200ft incline over 1/4 mile. Last I checked, I wasn't super-human. So it seems the walk activity has issues. Or... anything that generates a VO2 max result. Perhaps the CPU is getting too taxed on some calculations and it cannot keep up with the sensor. It isn't like these CPUs are speed demons.
Garmin, you may wish to look into the legitimacy of these complaints. It may not be the sensor code, but something else bogging the device down.

my first fenix 5 had problems with every activity except run, i got a replacement unit and now only walk activity is low

Do you observe any relationship between low HR and watch face you use? I used to have Crystal watch face which is showing HR 24/7. When I switched to default watch face ("analog") and started one of problematic activities it worked fine. It might be coincidence and need to be confirmed later, however I am just about to return my Fenix to Amazon (after replacement same issues).

Do you observe any relationship between low HR and watch face you use? I used to have Crystal watch face which is showing HR 24/7. When I switched to default watch face ("analog") and started one of problematic activities it worked fine. It might be coincidence and need to be confirmed later, however I am just about to return my Fenix to Amazon (after replacement same issues).

I only use stock faces. Optic hr is not good for training. It sucks on garmin watches. Hr strap only way. My appple watch and xiaomi band 2 have better ohr reading during walk.
Last garmin watch for me

I only use stock faces. Optic hr is not good for training. It sucks on garmin watches. Hr strap only way. My appple watch and xiaomi band 2 have better ohr reading during walk.
Last garmin watch for me

Stock face (without HR) decreased number of trainings with random HR, however Garmin's OHR still sucks. I fully agree that wrist HR are not designed for accurate training readings, however if OHR mistake is more than 100% (for very long time 60bpm on Garmin while HR is 160bpm) it means that Garmin sells trash. Tomorrow returning my Fenix 5s to Amazon. Goodbye Garmin!