Saw this in prod some time back with zk assignment
On clean startup, while master was doing bulk assign while one of the region servers dies. The bulk assigner then tried to assign it individually using AssignCallable. The AssignCallable does a forceStateToOffline() and skips assigning as it wants the SSH to do the assignment
But the SSH wont assign as the region is offline but not in transition
In zk-less assignment, the bulk assigner invoking AssignCallable and the SSH may try to assign the region. But as they go through lock, only one will succeed and doesn't seem to be an issue.