It is unusual for SC not to work if it is a genuinely retail state Xbox.
You are/were using an authentic original PAL version of the game I hope. I've used three different PAL ones (original release, Classic and one that came bundled with my first Xbox) all work.
You should have two saves - the exploit and the, larger, installer. How did you get the saves to the Xbox?
Flash drives can be very, very weird when used with the Xbox and I've had some that only transferred some files before going missing. It is rare when transferring stuff from a flash drive to the Xbox but it does happen. So, in Memory/Game Saves check the number of blocks used by the installer save is the same as that shown on the flash drive or other transfer device you used.
You could try again with SC but I'd suggest removing everything you've already done and trying from scratch with a different installer package like Rocky5's XST or SID 5.11.
