Intensive minutes did not count properly on different activities

Hello,

I have two activities on the same bike and with the same equipment, but the activities show different intensity minutes, for example 1 minute. Can someone explain why a harder workout shows lower values for calories and intensity minutes?

The correct one:
https://connect.garmin.com/modern/activity/20030919008

Incorrect one:
https://connect.garmin.com/modern/activity/20048637748

I would be very thankful if someone can explain what happened.

 

Kind Regards,
Mat