My system is not EFI so will not allow for the solution above.

I reinstalled the backup linux on sdc2 then the primary linux on sda2
This was so the primary on sda2 would be where Grub was installed (thinking it may be an old grub issue that required it to be on the first drive)

Grub is now working again
Grub provides options to boot the primary linux, windows and the backup linux
I can boot the primary linux and also windows
The backup linux is booting to a terminal mode, emergency login.

I worked through the boot.log and is showed a list of snapshots that were trying to load that all failed
I opened the sdc2 linux fstab and remarked those out and rebooted.
It is now working.

Thank you for the help and suggestions