Hi egon2003,
I suppose you try to use a Advanced Mode in UEFI Bios?
have you check if there is something in ''boot services" and "runtime services" ... causing the problem...
UEFI does not specify how POST & Setup are implemented. UEFI is an interface.
The UEFI Bios have just a standard USB drivers...
So when you plug a device in usb port AND if the Device need a drivers ( the device drivers needed to run).
It will never work I think before the operating system is loaded.
Otherwise for oc your system ... remove a device from usb port... boot to Post and (try if possible connected a Device on USB port Just before OS system procédure started... ( Check if is okay for your mobo ... connected to usb in this condition) ... Maybe wait a comments by other members...
This is just my opinion...
Gloup_Gloup