Well, it appears then it is not a thing and we have been unlucky, as have a few others. The conductor said that it does happen and that the "correct" seat assignment is the one on the app. Some of my reservations were made by others, not on my app, and I even had a few
paper tickets. Maybe that interface is the issue. Whatever, I will now make all of the bookings myself on the app and see if that ends it.