Epix 2 heart rate values too low and then jump high. Impossible to train to heart rate.

Can you provide a orientational deadline until this is planned to be fixed (since it is obviously not isolated case)?

Is it recognized that this issue was not as emphasized before the software updates or do you consider that this is due to malfunction in particular watches affected (even though there are unusually many of them affected, even from other models)?

I had a comparable issue with a previous firmware, however, the 16.22 is working very well for me.

What I have noticed is that if I leave my watch to loose around my wrist, the HR becomes unreliable.

Furthermore, I have noticed that when it is cold, and I go a for a run, I experience issues in the HR. This is either a physical effect on the watch itself (hysteresis??), or a physiological effect due to my blood flow to my extremities changing as a result of the sudden transition from 20°C to -10°C. Keeping the watch under my fleece jacket until I was warmed up again solved the issue. Of course I then cannot see my performance, but these are reported via the headphones every kilometer.

Garmin-Laurie the same behaviour occured again today, as it has with every run activity since the update. Chart below. I also keep getting "maximum heart rate adjusted" notifications after runs which I never used to get.

I hope your engineers realise this should be a top priority. This is a huge, repeatable error with a basic core function of the watch.

At a guess, I'd say there's a bug in the predictive model used in the HR state estimation algorithm. I trust your engineers are looking into this urgently. I can provide multiple examples with the exact same behaviour since the update.

Garmin-Laurie said:

as yet, do not have enough data

"still investigating reports", "do not have enough data"???

this is - at least - a year long bug, reproducible across different devices: 
HR glitch - wrist HR is completely unreliable - Forerunner 265 Series - Running/Multisport - Garmin Forums

and you are sayin' that you "do not have enough data" and engineers are still investigating reports?

let we do the hard work instead of your engineering team, shall we? you know, this bug can be reproducible at 100% percent, so I did it for you, here is how:

Description of the issue:
In case of lack of reliable HR reading from the wrist HR sensor, the device are hallucinating HR values.

Environment, device:
- Epix Pro, sapphire, 51mm
- room temperature, dim indoor lighting (no direct light to the HR sensor)
- time: just before writing this comment
- activity: Cardio

Steps to Reproduce: 
1) strap on your watch very loosely
2) start the activity
3) start walking around slowly (making sure your HR won't change significantly), but moving your arm as you would do in running
4) keep this for approx 2 minutes
5) save the activity
6) post the result HR into this chat

Expected Result:
During activity: a "dash" mark on the display in the HR data field, as a sign of missing reliable HR reading from the sensor.
In the saved activity: missing parts in the HR chart

Actual Result:
During activity: fake, arbitrary, hallucinated values on the display in the HR data field
In the saved activity: crap data in the HR chart

See yourself:

Your engineering team does not need new data or reports. Just test your own devices for God's sake, it would not take 2 minutes to test!

That solves the issue for me.

Fortunately, the issues only occurred incidentally and only in the winter when going from warm to cold. So the last couple of months I have no issues and I keep my watch on at all times!

An issue needs to be reproducible. Incidental issues cannot trigger a fix.

In your case you mention a potential cause

Steps to Reproduce: 
1) strap on your watch very loosely

SO, for God's sake, strap on your watch tight, and the issues may be gone. takes 5 seconds.

I'm having the same issue, some days it works some days it jumps. It's the same run every day. It's only been happening the last week

I am afraid that you did not get the point. 

Reading errors and less reliable readings do happen in normal scenarios as well. The root cause of this issue that the watch start hallucinating fake HR values then and it can stay in this state for minutes.

The issue is not the unreliable reading, the issue is interpreting invalid data as valid data.

My demonstration proved exactly like that - if there are unreliable readings then the watch starts reporting fantasy HR values.

Wearing it tight will help in the vast majority of the cases, sure - that is not a question. But when it can't help, then, boom, you will have fake HR data for a prolonged period and half of your HR data is just pure garbage, including all your other metrics.