I am not getting intenstiy minutes everytime

3322293
11 days ago

I have 2  nearly identical cycling activities. 

Kit:

Garmin 540

Rouvy

Wahoo Kickr Core

Garmin HRM

Data, HR going to 540. Watts from Rouvy to 540

1st activity generated 50 IM, the second 6 IM. 

why, is there a way for force recalc?