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- The Surface Pro 4 has a i3c HID bus.

- Inability to shut down tablet w/o holding power button -> Borked ACPI tables, especially DSDT -> UEFI firmware update slipped in there?

- Excessive fan usage -> Same as above

- ME driver problem -> EFI variables (I've seen that these can affect ME on my laptop too)

So for the reasons above, it's probably screwing about with UEFI firmware or its EFI NVRAM variables.