This morning Windows 8 failed to resume from the sleep mode I put it in yesterday. Instead it launched linux (which is in the default EFI/Boot option). I did manage to get back into the BIOS setup and it turns out the list of boot options had been wiped again, with only network boot remaining. Somehow it was falling back to EFI/Boot/bootx64.efi, instead of the default Windows partition that it used to pick in the past, when it was completely ignoring the whole ESP partition setup.
I almost don't dare to ask, but when can we expect A15? What other alternatives do we have? Sending back the whole machine doesn't make sense when the replacement will likely have the same bios/problems.