Intel X550 Issue - SIOM Module

[NiKiZe]

I can not see any reason for an ok embedded script to be causing this... the reason being what actually happens in the code when an embedded script exists.
The relevant code is at: https://git.ipxe.org/ipxe.git/blob/133f4...oot.c#l592
So the only alternatives here logically is a bad script (which it isn't if the same script works with legacy builds) or some kind of memory corruption.

In the video what I saw was a restart or exit from iPXE - I could not see any type of crash.

If it is a restart .... could it be some kind of watchdog in the firmware that triggers restart?

Just realized you have not given any boot with ipxe.efi and the output of ifstat.
One thing that you might want to try is to create a build of ipxe without any valid driver for your nic, for example build tg3.efi which is broadcom - this will make sure that there is nothing during the access to nic that is causing the issue.

Also make sure you are building yourself, from clean sources, and without any modifications. (it's to easy to change rom-o-matic configs to non defaults, so not a good source to use when doing debugging)