Stuck iPXE initialising devices - .efi pxe boot

[philthynz]

I am using Grub to boot ipxe, and then to load wimboot. On some newer Lenovo laptops, specifically the L470 ipxe stops at "iPXE initialising devices"

The pxe server is using grubnetx64.efi.signed as the net-boot server, and the dhcp comes from the router. This works fine for Grun booting most debian based OS's and tools over the network, and works fine with most of our hardware for ipxe.

I use rom-o-matic.eu to build and embed the script. In the driver for the L470 is an "Intel I219-V", which is listed in the rom-o-matic drivers list.

The script is:
#!ipxe
dhcp
kernel http://192.168.2.8/grub/config/win_pe/wimboot
initrd http://192.168.2.8/grub/config/win_pe/BCD
initrd http://192.168.2.8/grub/config/win_pe/boot.sdi
initrd http://192.168.2.8/grub/config/win_pe/boot.wim
boot

And launched from Grub with:
menuentry "Windows PE Test" {
location=$configpath/win_pe
chainloader $location/ipxe.efi
}

I tested to see if anything else boots with the "Intel I219-V", and some tools work fine, some debian based OS's fail to load with the error "Waiting for ethernet card(s) up... If this fails, maybe the ethernet card is not supported by the kernel 3.16.0-4-amd47"

Clonezilla boots fine on the L470, so i presume the BIOS config is fine. It's set up UEFI, CSM disabled and Secure Boot disabled.

I tried to do some small tests, such as "echo test" in the ipxe embeded script, again is still doesn't get past "iPXE initialising devices".

Can anyone help debug this with me? Or know how to resolve this?