K4 Kindle 4 randomly resetting to snapshot (where does it store it?)

I have this Kindle 4 Non-touch Non-4G 4.1.1 who froze/stopped working and I unbricked it by pressing the power button for +10 secs and it rebooted and started working again. But it continually randomly froze again, rebooted by itself or performed a “reset factory settings” by itself. So I decided to clean it up.

I deleted everything in it, I deleted the hidden system files, I did a FULL FORMAT. The Kindle now is clean and pure, but the thing that leaves me flabbergasted is, if I perform a “Reset to factory settings” on this clean, pure Kindle, it shows up the old books and old document files that I deleted! :eek:

Not all of them, but it’s more of a snapshot of my Kindle content of some months before. It’s like if it’s going back to a “restore point” created months before. And if I delete the books and documents again and perform a “Reset to factory settings”, it goes back to that snapshot/restore point.

So my question is: where is it storing this content (books, documents, collections details etc.)?

-There is no hidden partition on it
-It is not taking them from the air as its wifi (and my router wifi) is turned off and it’s not a 3G model.

Last thing: I tried entering the diagnostic menu by putting the ENABLE_DIAGS file in it and rebooting but it didn’t work (it booted like usual and deleted the ENABLE_DIAGS file)

Davide