Long time to boot into SCCM

Hi,

I'm having a strage issue when PXE booting a new device: HP X2 Elite 1012 G1 Tablet - using Legacy Bios, using the USB-c dock.

I have the realtek NIC drivers and the thunderbolt dock drivers added to the boot image. Its shipped with BIOS is v1.0.16 and have tried with BIOS 1.0.17

So I'm able to:

PXE boot and get an IP

Download the boot image OK

This is where it gets stuck: It displays windows symbol on screen and sits here:

But surprisingly if you leave it sitting like this for approx. 2.5 hours it will go through into System Centre:

I have never had this issue with any other hardware. It goes through within a few seconds.

Any advice on how to troubleshoot this?

Thanks.