I’ve been kind of busy getting big project at work to the finish line, but I’ve been thinking about attempting to use (as a test) other boot loaders like grub or elilo to see if they handle uefi booting better than ipxe. But right now its not clear if we have 2 or 3 different issues. Is it the built in uefi bios, the boot loader or the current FOS kernel that is having problems. It may be a combination of all three (which makes it even harder to debug).
At this point we need to eliminate 2 of the three possibilities to work on the third.