The original microsd cards seem very unreliable and old.  I had same problem.  Upgraded to a new Microsd and it worked fine.  Those supplied with the apollo II seem old and unreliable.  16GB was outdated a while ago.  Old cards sold at a discount in the major outlets are 32 and 64GB.  I bought an ONN and PNY 32 and 64 gB flashed v 2.0.6 and they worked fine and are very stable. They are slower microsd cards but time to boot is only 25% slower and while operating, OS minimal speed difference vs a newer fast memory card.