Turns out this wasn't an issue with the Windows 10 installer, but from some corruption of the locale files in my EFI partition (EFI\Microsoft\Boot\{xx-XX}). I was able to resolve the issue by doing...

I have spent the last week trying to install Windows 10 Pro on my XPS15 9530 but it always fails as the installer is preparing for the first reboot with the message "Windows 10 has failed to...