Comment 9 for bug 1492801

You can move the file while still booted to Live USB or you can do it from WinPE if that is easier for you.

Backup the grub.efi file and then in WinPE CMD type diskpart then type list volume then select the EFI partition and type ASSIGN LETTER=F, then replace the file on F:

About Secure Boot, for it to work it needs to boot the shim.efi file that is located on EFI partition, I am not sure how to make it work with the replaced grub file and the shim file, but you can experiment with it.

I hope this will be fixed in next release.