Im dual booting Ubuntu/Windows.
So first of all booting windows by selecting the windows boot loader from UEFI works fine.
Im using EFI for both bootloaders.
Booting Ubuntu from grub also works fine, just booting windows from grub does not. The screen just instantly returns me to the grub screen without any error.
This started after I re-partitioned another hard drive from my laptop (running Arch) and accidentally ran update-grub by auto-completion while it was connected. This created a boot entry for arch, which I removed by running grub-update again after disconnecting that drive.
I added paging=1 and debug=all to grub.cfg to try and debug the boot sequence but didnt find any errors.
Has anyone got any ideas? Im happy to provide any details needed. Thanks for any ideas!