Backed up Original PSO Saves on Flycast/Retroarch

[Nnooo]

Hi There,

I have, today, backed up all of my VMUs to SD and imported them into Retroarch so I can continue playing my games if/when my DC dies.
All of my saves work except my PSO saves.

I have tried:
1) Entering my PSO v1 SNAK from my original PSO v1 disc
2) Entering my PSO v1 SNAK from my original PSO v2 disc

The game accepts either code fine but always gives the error "This file cannot be used to play the game".

My DC is PAL/EU
My Games are all original GDRom discs (PAL/EU)
The games I have in retroarch are all EU GDIs

I have removed the dc_nvram.bin each time I have tried this to clear the saved SNAK.

Is there possibly a file on the memory card which I have missed or is invisible I need to copy over because the SNAKs I have are all the original I used when I played as is the Dreamcast and the saves still load fine on it..?

Any help most appreciated.

Is there a way to dump the flash memory of my DC and use that in retroarch along with a dumped bios?