Next time I run into it I assumed this is because if there is already a backup and you try to mv to the same exact backup everything comes tumbling down but I'll check it out again and if it is different file under a diff bug
Next time I run into it I assumed this is because if there is already a backup and you try to mv to the same exact backup everything comes tumbling down but I'll check it out again and if it is different file under a diff bug