Not sure what else to say, really. I can be coming out of a portal, mounting my horse, dismounting my horse, exiting a dungeon, and so on. When cross-platform is enabled, the game eventually crashes to desktop. Can be after 30 minutes or after 60 minutes. But it’s guaranteed to happen.
If I disable cross-platform play and cross-platform communication, the game just works reliably i.e., stops crashing. Zero crashes.