There are 4 sensors on the pillar that detect the magnets, staggered left/right from top to bottom to pick up the 2 doors. Any one of them triggering will trigger the door sensor detection logic. They each have a small LED that in a darkened room you can see turn on when you bring a magnet near.
If one side of the enclosure is never triggering the door open detection that sounds like a flaw to me and you should consider reaching out to support.