Heart Rate Way Wrong

Well, overall I give the fenix 5x+ pretty high marks in general, however I have had several specific issues with the HR monitor when I'm working out hard and my heart rate goes up. I can repeat it anytime I want on the indoor rowing machine. As I get into my intervals and my HR goes above 140 the reading steadily declines as my HR is actually increasing (probably to around 170). The reading ends up below 60 while I'm out of breathe. As my HR drops down to around 140 the 5x+ starts rising from below 60 and eventually syncs up again. VERY FRUSTRATING.

Got exactly the same behaviour, in my case during some hiking activity. If I restart the watch, after it droped down to 60, it shows the right pulse again. I contacted Garmin support twice and they offered me to exchange my 5x+ to a refurbished one, although they state, that there is no known problem.

I even forwarded them links to the various forum threads, because I'm actually a bit concerned that I send my watch in and this hole exchange is useless. The strange thing is, that normal 24/7 tracking is working flawless, it only happens in my case during hiking activities. It even happens sometimes that I do not get that behaviour within 1 out of 10 hiking activities, but in the other 8 I'm getting always the same problem.

As I'm a tech guy myself, I cannot really believe that this is a hardware issue, where exchange might help, so I'm still not 100% sure, that exchanging the watch will help....

Got a replacement as well after garmin support insisted for exchange, despite my concerns.....so as expected, new watch behaves the same way as the old one....heart rate way too long and after some time drops to resting heart rate level during hiking.....so I'm back to the chest strap HR monitor and use the HR of the watch just for 24/7 all day tracking...

Do you know if the Fenix 3 HR has a different OHR sensor then the 5x Plus? I always assumed the sensors were terrible across all Fenix watches, but this doesn't seem to be true. I thought it might have to do with the weight of the watch. I just happened to look at my friend's HR data from a MTB race we both did. I was using my 5x plus w/ Garmin HR chest strap and he used his 3HR on his wrist without a chest strap. His HR data looked to be what would be expected during this race. I haven't used my watch on my wrist during a race, but quite a few regular MTB rides/workouts using only the OHR. My results never come close to being accurate. It always reports seriously low HR numbers. Never accurately mimicking the actual effort of the ride. I was very surprised at my buddy's results as I have never seen anything like that with my 5x plus OHR.  I've tried moving the watch up and down my arm, switch to the other wrist, tried tight, medium tight, loose, shaved my wrist, and a few other things. Nothing changes the horrible results! 

Changed from Fenix 3 (without OHR) to Fenix 5X Plus. I used the Fenix 3 with a strap for several years and thought I could avoid the strap with the OHR. But unfortunately its not working. First 3 runs with OHR my HR with 20bpm higher in average. Also using it during cycling its not working probably. 

When you wear it very, very tight to your wrists its a bit more accurate but then it gets very uncomfortable :( 

This was not what I expected when I bought this quite expensive watch!! I thought this would be a big step forward. 

Im using it now with the old strap...

Sorry, but that’s what I would call really poor research before purchasing.

There is always someone who knows better!