Reading other posts, not specifically related, but caught my eye - the 'bad' SD card vs 'good' issue.. Fwiw, my M10's SD card is SanDisk Ultra II sdhc c4 8Gb
I've used it a lot with chdk. Lots of partitions, BOOTDISK and SCRIPTDISK written to it..
I will test M10 again, same failing tests, but with *brand new* card.
san disk Extreme Plus sdhc-I c10 16Gb
Try to rule out a garbage sd card. Will advise if similar results, will capture romlogs if any.