@Paladin1 Thanks, that explains the registration error. Registration reads the machine’s disk, so it needs a disk attached. With no disk it stops with that message every time. That is expected, so you do not need the debug task.
For your question: neither. Do not reinstall anything yet.
The BIOS boot mode on this machine applies to both the network boot and the installed OS. Your image is a UEFI install, so this machine has to network boot in UEFI too. We can try a different iPXE file for UEFI that loads its own network driver. That can avoid the firmware error.
On the FOG server:
Edit /etc/kea/kea-dhcp4.conf. In the classes FOG-UEFI-64-1, FOG-UEFI-64-2, FOG-UEFI-64-3 and FOG-Surface-Pro-4, change "boot-file-name": "snponly.efi" to "boot-file-name": "ipxe.efi". Run sudo systemctl restart kea-dhcp4-server. Set the target BIOS back to UEFI and network boot it.Tell us if you get the FOG menu or the same ASSERT. If it fails, change the file back. A re-run of the installer also puts snponly.efi back.