UEFI boot and sanhook

[NiKiZe]

What exactly is it that you want to do?
iPXE san* devices in EFI is exposed via the efi_block interface.
Booting from this works fine as you wrote.
(sanboot is just sanhook with the extra "tell firmware to boot it", so should be no difference)

When these block devices is connected it is up to mostly the efi firmware to do the right thing.
In the case of the shell it should be available there as block device, partitions and EFI compatible filesystems, if there are any that is.

I would also suggest to listen to the wire (tcpdump or wireshark) and see what is going on there.
One possible reason could be that when you start your applications the network layer is interrupted.

You might also want to provide more details on what you are doing and using (exact commands) in such a way that someone else would be able to reproduce this.