Major version upgrades occasionally break things because they're a new feature release but are then trying to migrate configuration from the existing system. Bu

Major version upgrades occasionally break things because they're a new feature release but are then trying to migrate configuration from the existing system. But the same thing happens with "atomic" upgrades if you're trying to migrate existing configuration, because the bug is really in the migration system that didn't properly handle that configuration variance, not because the packages aren't upgraded atomically. Which is why phones sometimes do break on major version upgrades for the same reason.