for those having problems flashing their rootfs
I have now an N9 that have this problem
i got the "mmc: sfdisk returned status 1" error
also when using the moslo kernel to mount the eMMC
I got errors on accessing the partitions
I remembered i had a similar problem happen on my last N900 (flashing the rootfs failing)
the solution was to remove the battery for a one day or two
and the retry flash and it worked
the N900 was also because of battery drain
so somehow the battery cause the eMMC to not work proprely
I have disconnected the battery from my 16G N9 ( I bought another one with 64G )
and I'll report in 2 days