Epix Pro: Occasional HRM error - how to solve?

It happens to me too. Pausing the training and starting it again seems to solve this temporarily.

Welcome to Epix Pro software issues. That's not a hardware issue, it's the software. For me it's for half a year now and up to now no software fix. Use a chest strap if you want reliable results.

With actual software the optical HR sensor delivers only crap. There are more than on thread about this issue in the forum.

For cycling activities it has been happening almost every time for several months now, where the OHR reads way too low at the start.  This could be just for a few minutes, or up to 15 mins or more.  For this reason I always use a chest strap when I am doing shorter workouts where accurate HR is more important, like power-based interval sessions.  If I am doing a more casual workout or long ride without the strap I just check the OHR reading constantly until I am satisfied it is tracking correctly.  If it does not "catch up" within a minute or two I just disable the OHR sensor then re-enable it (without stopping the activity) and that usually does the trick - HR immediately jumps to a sensible value.  Once it is tracking correctly I don't have any problems with it again during the workout.

It has been suggested numerous times by various forum users that it is just variations in how people are wearing the watch, or how they hold the handlebars, or variations in their skin colour/temp, or the weather, blah, blah.  but the reality is that I can keep my watch hand exactly where it is on the handlebar and just keep riding at the same effort/cadence while I just toggle the OHR off/on and it immediately jumps to the correct HR.  So while I have no doubt that how the watch is worn etc can have an effect on the OHR in some instances,  that is categorically not the case in my experience.  Furthermore this was not a problem for the first 6 months or so of owning the watch.  And with my old Instinct 1 never suffered from this problem.  

When the watch has this issue at the start of an activity it more or less just sits at around low to mid 80s and doesn't change by more than 1 or 2 bpm, even on steep hills.  So it is immediately obvious.

My suggestion would be to invest in a chest strap if you need reasonably accurate (or at least consistent) HR data, and failing that keep an eye on the HR at the start of the activity and toggle the OHR off/on if it looks too low after a minute or so.

I agree with the others except about buying a chest strap. I do find that stopping to turn off the HR sensor for about ten seconds will seem to reset it so that when you resume the workout it picks up your HR accurately. Yes, it's a bummer to have to interrupt a workout, but Garmin doesn't see fit to fix the problem.

How do you deactivate/ activate the OHR sensor fast during training?

Going into the settings during a run would drive me totally mad and would get me out of training so that completely useless to go on.

As other said, this is know issue that Garmin keeps ignoring in spite of numerous user reports and proofs about it. Months ago they said they would investigate (for Fenix 7 and Epix) and fix it (for Forerunners), but they just ignored and keep ignoring it. The issue affects range of Garmin watches, not just Fenix 7 and Epix.

You are not missing anything although I am not sure what you can do. Others offered workarounds but those may sometimes work and sometimes not, and may not be very convenient. In any case, they are workarounds for key feature of the watch. Thus, I suggest not to buy Garmin chest strap to work around this issue, not to give them more money since they broke proper HR tracking on their watches.

I agree with Vizi that one shouldn't buy an extra HRM chest strap. I had the luck that I still had my old HRM Dual from Garmin.

If I didn't had that I would have definitely reclaimed my money and had already switched to another brand. Like this it's still acceptable for me, but buying a new strap to make the watch work as it should is not acceptable at all.

Garmin has to fix it's software!

Finally, since they just deny the problem and don't do anything to solve it I fear that it's even some hardware issue or their software team is just totally incompetent.

It is easy enough to do while riding along at a steady rate on a decent road, especially as I have done it plenty of times now so I know the menu structure to get there quickly.  But it is still a pain, and if I was riding single track on my mountain bike I would probably just stop while I did it - but I usually have the chest strap for those rides.

It is more frustrating to do while running.  I always struggle a bit with the display when I'm running and the watch is bouncing around because my old eyes are not quite up to it sadly.

Interestingly, I have noticed that it has been much better over the last couple of weeks or so.  I haven't had to do anything with the OHR on my casual rides as it has tracked really well from the outset.  Maybe one of the last couple of updates did something surreptitiously under the hood ...

Yes I too agree - in general we shouldn't need a chest strap.  Maybe for intensive interval stuff or "serious" training where accurate HR is more critical in the scheme of an overall training plan, but not for "everyday" activities.  Fortunately I still have my (really) old chest strap from my Forerunner 310XT days and that still works fine. 

Pause the workout, go into settings/sensors/wrist HR. Turn off. Wait a few seconds. Turn on. Resume workout.