Originally Posted by e-ink
I'm glad I could help.
As for the cause of your issue I wouldn't have any idea.
See if the pre-installed "@Test Mode" app is able to reboot / shutdown your reader. It doesn't show up on home screen page #3, but you can access it via a launcher.
I've done a full image recovery, when backed to original version,everything going well(including recovery mode),when backed to re-partitioned version,system update went well but recovery mode(usb serial console) is not usable,but other problems were gone,it could just properly shutdown and update the system as usual .Also putting rupor's recovery image under root of sd and trying to get into recovery mode it just works. Doesn't know the reason but it really just help me out of the problem. Right now I'd just prefer stayed with re-partitioned one without original recovery mode access.