before any action ... comes diagnosis: please fill in missing pieces: - SDD's, HDD are formatted GPT? or is the dinosaur using MBR? - is your computer configured to boot UEFI-style? Or are you still using BIOS-style/compatibility-mode? - can you show (and comment) the output from lsblk and (sudo) blkid? - did you look at all the grub.cfg files (in different systems)? Anything particular? - Are you able to use grub command line in case you would need it?
My first guess would be, that sticking to /dev/sd?? device names confused yourself, the OS and maybe even grub. i recommend (mid-term) to switch to some other ID, like PARTUUID, or such in order to prevent confusion. But first things first: I did not really understand the problem, you are running into, which certainly has an easy fix, once it reveals itself fully. DdB
