Low hr activity

I have exactly the same issue as Tyler described. I did hard reset - it is better but still not good. Before hard reset the issue occurred during every second activity, after hard reset 20% of my activities are affected.
Before hard reset frequent soft-resets worked for me, now if problem occur nothing helps.

I opened the ticket with Garmin support and their only solution is to send the device back.

Same here.... fenix5 75bpm vivoactive2 89bpm!

I've had a Fenix 5s for two months and HR measurement is very erratic during an activity. It records it fine otherwise, but during a brisk walk when my HR might be 100+ it might only show 60 or less. This morning for example it started off fine, but suddenly after about 40min it dropped down to about 60. At one point it even reached 51! Two days ago on a much faster walk (it was raining as well) my HR recorded more like I would expect - perhaps even higher than it really was. Maybe it's something to do with arms swinging. When running one's wrists might be higher than when walking.
I have to say that wrist-based HR measurement is often erratic and spending more doesn't seem to make much difference. A Fitbit Charge HR I was using three years ago always understated my HR during exercise, but at least it didn't give up altogether! If I use a chest strap I get an accurate measurement of course.

I pay 200bucks for a vivoactive2 and it works. I pay 500bucks for the fenix 5 and it sucks.... cant belive it....

I too have been struggling with this issue. It seems to have worsened after the fw update to 10.0. What I have found recently is that I start the walk activity, while it is searching for gps(I start it indoors) I loosen the band, move the watch higher up my wrist(about an inch or so) and then tighten to the point of almost discomfort. Once I have gps lock I start the activity. After about 10-15 seconds I scroll to the HR screen. This seems to help but it is not 100%. For the $ we all paid we shouldnt have to "hope it works". Ive debated rolling back to fw9.73 but then I have to disable auto update etc and I get nervous messing with fw for fear of turning it into a brick.....Heres to hoping the next fw fixes our issues.

I think it have something too do with speed. Higher hr downhill on bike than uphill. Weird? when walking hr is wrong. When i run hr is good. If i walk and shake hand like if i run hr goes up.

After 90min workout im walking to come down.... 120bpm... 10mins later while walking... 60bpm.... .....

Got a replacement unit from garmin. As soon my arrived at garmin. Will see how this one work

Tested the New one. Low hr in activity.
Same walk without activity higher hr. Software 8.0. Dont know what more to do.

Updated to 10.00. Did a elliptical and the watch worked great. Looks like my old was broken