It makes me wonder whether Windows updates could cause / resolve something like this. I always assume the BIOS/POST sequence is too isolated for that to be the case, but with UEFI there's much more access from the OS - to the extent that updating a BIOS can now trigger a process in Windows on next boot (like asking you to install motherboard software). And I remember that Windows malware that could exploit your BIOS boot image. So perhaps it's possible?