I have a MacBook Pro 15 (2018), I am trying to migrate my Bootcamp volume to an external SanDisk Extreme PRO 512GB SSD. I can create a backup image from volume, and then restore image. This works fine, but when I try to boot by holding down the option key, it boots and then get the INACCESSIBLE_BOOT_DEVICE. I have tried all the suggestions on this forum but nothing works.
I am running Catalina 10.15.1
Any help would be appreciated