I have had this happen twice in the last month.

As far as I can tell, it happened when I changed the setting that tells the screen to stay on while the unit is charging. I would pick it up the next morning and it would be flashing like you described. I turn it off and on and then everything is fine. I turned off the option to have the screen always on while charging and it did not re-occur, until I changed the setting back to having the screen on while charging again.