ROM-Reader for Super Nintendo / Super Famicom Game Cartridges

I had a quick question. I have been trying to dump a prototype DMG-MBC5-32M-R-FLASH, has anyone been successful using the Sanni Cart Reader? I always get Checksum Failure when reading this cart. It plays fine but I just cannot dump it.

I haven't had any issues with other ROMs I have dumped and I am able to Read and Write NP Power etc.

Thanks