Fenix 5S HR monitoring is grossly inaccurate?

I got my watch about a week ago, installed all the proper updates, and have been using it daily. I have noticed an issue with the HR monitoring across the board. I primarily do CrossFit, which means my activities vary from lifting to running to random cardio movements to strength. I can push myself to the brink and be lying on the floor breathless and the watch is reading my HR as something like 110 or even as low as something like 84. The only time I seem to get any semblance of accurate HR is if I am actually running or jogging, with my arms pumping. When I check, I will then be in the cardio zone with something like 140-150. Other than that, my watch does not seem to pick up changes in HR accurately. I have tried the strength setting, cardio setting, etc and was starting to think maybe I needed to update my software, but it is up-to-date. I have also tried re-positioning the watch on my wrist, as well as both tightening it and loosening it. Nothing I have done has seemed to improve the HR monitoring.

Note: I previously had the Forerunner 225 with HR monitor, so I am familiar with the wrist HR monitoring. I would have issues from time to time with that watch's HR monitoring, but not like this. I recognize that wrist HR monitoring is less accurate than a chest monitor, but I have upgraded my watch (at a hefty $$$) for what appears to be less accuracy.

Can anyone help? Is anyone else experiencing this?