When Kim-Remi Kjesbu (Creator of the series) was about to film the transition video on the segway, he destroyed his camera. The same camera that he has filmed and was supposed to film all the episodes with.
He was about to go on the segway, did not get the balance, got out of control and crashed with the camera that was on a tripod. So he got the owner of the segway to film with the phone of Kim-Remi, an iPhone 7. That's why the transitions are filmed vertically.