my mi band 2 was more accurate than my Fenix 5
Different weight, different size, different sensor, a watch and a band will move around your wrist differently based on design. It all comes into play.
I do not agree.
I have the same issue and now 3 times it completely stops altogether during activity. I also wear a chest strap and it still stops working. When I took the watch off to see if the sensor was still on. The sensor was completely off. This watch is less than a month old.
If you begin an activity when you are wearing a paired chest strap, your Instinct OHR will turn off and the watch will read only the external source. If you are seeing these "stops" are you always wearing a chest strap? If so, you might have an issue with the strap (battery ??) or the connection.
My Instinct seems to keep reading from the chest strap even after the activity has ended, until the strap is removed and distanced from the watch.