MMC device number has been swapped on newest OS Image, the new OS Image has this fixed. Since i don't know which Image is in use and without serial console logs is hard to give some advice. Sorry, but what puzzled me is that you say you can boot from eMMC with an empty SD card inserted, that's what I suppose he wants to do. Is this really possible or i misanterstood?   Did you really follow the instructions printed there? Where it says you need to create a new partition?