Intensity minutes not correct, with photos

As per the title. Intensity minutes are not calculating correctly despite appropriate settings. 2 examples below. 

Settings are set correctly through the app. 

Example 1. 

I was in zone 2 for about 5 minutes, yet the app records 36 minutes of moderate activity. 

Example 2. 

As we can see, I should have 0 vigorous minutes recorded as my HR was not in zone 4. 

A couple of extra details:

- My device is on the latest version. 

- I use an Armband HR monitor and connect it through my instinct. Maybe this is the cause of the faulty readings?

-My interpretation of the data. Although I have my intensity minutes set to 'in zon'e', maybe I'm missing something as to how Garmin processes this 'in zone' data. 

Any help is appreciated!