Yesterday evening opened the box, registered it to my Amazon account, copied couple of books from the Cloud, and copied couple of DRM removed books from the hard drive.
While testing that every book works, got into one DRM free book that refused to open (the book remained opened to the first page, and the device was stuck). Successfully rebooted, deleted the book from the menu, copied it again using the cable, and the same result (azw3 book).
Did a format change in Calible, copied it also as .mobi and .azw1, and got into this "Repair Needed" error screen.
If there is any other procedure I could try, I would appreciate, because replacing the damaged unit for sure will take at least couple of days..