I figured out a workaround to the PSX (and DS) Savestate crash
The problem is those Core dont like loading from the default location they are saved to.
What you need to do is change the Save and State path to .\ (the same path as the Cores folder)
First watch these 2 vids.. (first one shows how to create folders/move multiple files) do what it says but also create SAVE and STATE folders too.
Once you've made those folders, open Retroarch and navigate to Settings>Directory, scroll down to Savefile/Savestate and set the new path to the new folders you created. (don't forget to click "Use the directory" once you navigated to the correct path)
Once you've finished Quit Retroarch from the Main Menu to save, or goto Main Menu>Configuration File>Save Current Config
Done, you can now Quick Save and Quick Load on PS1/DS
This next Video shows how to set the correct permissions so you can keep using these folders after you restart your Xbox
This will all probably be redundant eventually but if you need to Quick Save on PS1/DS this should tide you over for now