pfsense mount root error after disk clone

I went the lazy route and cloned my SSD that runs my current pfsense (2.1.5) machine to create a backup machine with the same config. Instead of doing a fresh reinstall and copying the config. Both machines have the exact same hardware and BIOS settings. Both SSD's I used, main and clone are the same (size and brand). I used clonezilla to create the clone. During the boot of my "backup" machine I got the error: Trying to mount root from ufs:/dev/ad4s1a ROOT MOUNT ERROR Following the ?: It's so weird that this happend as it was a 1:1 clone. Also /dev/ad4s1a exists Anyone have any ideas how to: 1. Solve my current problem? 2. Avoid this during a clone? Thanks