So I tried to follow the procedure in the link in post #63, with one modification. I do not intend to modify init so I simply extracted the rootfs without uboot headers of the good PRS-T1, and tried to copy it to the other one.
What I did exactly:
1. Instead of extracting the rootfs from /dev/mmcblk I extracted from a Full backup file for both the good and the faulty PRST1s. The rootfs.img was 1Mb size. I tried
diff faultyrootfs.img goodrootfs.img
2. I created a newrootfs from the good PRS-T1 with the makeimage command as per instructions.
3. I ran
dd if=../newrootfs.img of=/dev/sdb bs=1 seek=5242880
, this time on the Reader and not on the backup file. (Needed sudo privileges).
4. Resetted the Reader… got stuck at opening book with a blank progress bar which didn't advance.
5. I restored the backup I had done of the faulty reader (after the problem began) with
dd if=Backup.bin of=/dev/sdb
and the Reader booted normally.
P.S. I'm on Ubuntu and the Reader internal sdcard is /dev/sdb so I replaced /dev/mmcblk2 with /dev/sdb.