Inaccurate heart rate measurement / Fenix 6 Pro Solar

Have you used a chest strap or HR is measured from the wrist?

From the wrist.

Any idea to how to fix this and/or address this best possible with Garmin?

Read the Garmin support notes about optical heart rate - of which there are countless links to them in the numerous threads that discuss this issue throughout this forum and on all other watches from all other manufacturers (with similar links).

If you are still unhappy contact Garmin Support directly.

If you are still unhappy get a chest strap to ensure reliable heart rate data.

If you are still unhappy with the results from optical heart rate, return the watch.

Return the watch if ohr is crucial to you. Search this forum for inaccurate HR and you will find countless of threads.

If you keep it, you will be disappointed to have spend so much money.

The most common cause of high OHR readings is "cadence lock" where movement of the watch on your wrist means external light enter the sensor in a rhythmic way with each step, and the watch locks onto this rather than your HR.

Larger and heavier watches are slightly more prone to this movement than lighter watches. The F6 Pro is a larger and heavier watch than your previous F5S.

What you can do to prevent cadence lock is to ensure the right positioning (on the fleshy part of the wrist, well away from the wrist bone) to ensure a good seal against external light, and that the band is snug to prevent movement. Personally, I find I have to have the band 1-2 notches tighter for accurate HR while running than I do for 24/7 monitoring, and if I see high HR while running, it almost always because I have forgotten to tighten the band before starting my run.

Nah. i tried that a long time ago. i even have nylon bands with Velcro so i can wear the watch higher on the forearm. Sometimes, the ohr is ok , but most of the time  it is not. I think the movement of the arm creates some kind of interference and screw up the readings. Usually, the ohr gets stuck at 80 while your real hr is way higher.

Same happening with me when running but notice that during bike ride it does not happen. The explanation of cadence lock makes sense. Try to make it tighter to your wrist. Sometimes not comfortable but fixed the issue for me. I am buying a Garmin chest strap to see if it fixes the problem.

OHR is useful technology for daily monitor. In "serious" sports as it is your case, where HR is a key piece of information, OHR is useless. Depending on the brand of the watch, type of skin, ambient conditions, cadence,...can be a bit more or less accurate, but in general you must use a chest strap to get reliable values.

Yes, true, but i had before fenix 5, 6,6x,7x.. instinct f935,945 and 965… only OHR in Epix2Pro causę the issues. My Wife is using Epix2pro 47 and is the same… same incredebly bad readings.