Heart rate wrong Fenix 5x

Hi all, I was out hiking with my wife today and I noticed my heart rate was 160-170. I felt out of breath and exhausted so thought it may be accurate. This was 6 hours ago now and it still bounces between 120-140. I removed the watch, cleaned it all down, even reset it and tried again... still pretty high. Put on my wife’s $200 Fitbit on the other wrist... 75-78bpm which is where it should be. I’ve tried on both wrists, cleaned it several times and whatever else but still the issue persists. 

reset the watch again, repaired it with the phone... 130-140 just sitting down. Fitbit still showing 75-78 or so.

has anyone else had a similar issue? How did you fix it? The intensity minutes are still climbing too... 550 intensity minutes today apparently.

I know that wrist based heart monitors will never be 100% accurate but it seems to be far less accurate than a watch 1/5th the cost. I have noticed high heart rates over the last month or so and I’m thinking it could just be the watch going faulty.