Unfortunately I can't even get to the ASA prompt as after the image is downloaded via ROMMON it fails when trying to boot for the first time (as shown in my original post).

I am having the same issue trying to flash asa984-lfbff-k8.SPA to my ASA5506-X, has anyone found a solution? I've attached the console output:rommon 3 > erase disk0: erase: Erasing 7038 MBytes ................ rommon 4 > ADDRESS=192.168.1.112 rommon ...