I don't know immediately what is happening either. One thing I am curious about is if it keeps track of the book status while reading. If you open a book, read a few pages and close it, does it reopen to the same place? What if you power off and on in between?
How did you do the factory reset? From the settings options? Or using the buttons? If the latter, did you make sure the device was powered off before doing this? The device must be powered off for these options to work.
When you tried the factory reset, what happened? It should restart, display a couple of different black screens with (from memory) an hour glass. From memory the two different screens will have something about restoring and installing software. Then it should boot to the usual smiley face and five squares. It doesn't sound like the first two screens are being displayed.
It does sound like something screwy has happened to the internal SD card. If the factory reset isn't working, then restoring an image of the SD card is the way to go. This means opening the device, removing the card and putting it into a PC. Then writing an image to that. Or getting a new card and using that. See
https://www.mobileread.com/forums/sho...d.php?t=209122 for some details. That is about changing the SD card for a larger one, but the process is basically the same. I have an image you can get if you need to do this.