I recently had a system which was passing all of the backup tests. However, when you attempted to boot the generated ISO from a VM it would crash and burn. It would basically give a kernel panic right after booting ramdisk0. Interestingly enough if you forcibly told it to boot with a bigger ramdisk0 it would get a little further. It would get past the ramdisk0 load, but crash out to a shell shortly afterwords (no errors).
initrd=/initrd.img root=/dev/ram0 rw ramdisk_size=512000 interactive
Anything smaller than 512K and it would do a kernel dump. Finally tracked the issue down to an old installed version of mindi-busybox-2.7.x.x. Upgrade your mindi-busybox version and you’ll be right as rain.
In my case, it was for a RHEL system, so I downloaded mindi-busybox-2.18.7.xxxx, removed the old version with rpm -e mindi-busybox-2.7.xxx –nodeps (can’t remember exact version) and then installed the new one with rpm -Uvh mindi-busybox-2.18.x.x.