Default [Q] One S rebooting after Nand Restore [Critical]

Hi.

I'm working on my girlfriends One S, which recently had:
  • Viper Rom 3.1
  • HBoot 2.15
  • Unlocked BL
  • Radio 1.15

After constantly getting random reboots, up to 20 times a day, I tried to S-OFF her device - without success - to update radio and kernel.

As far as I as know you need to be S-OFF to update kernel and radio, is it so?

Well I tried to restore her device from a NAND backup (which was using TrickDroid 9.0, or something), but now it is constantly rebooting while "system isn't responding", and it isn't asking for the PIN-code and not connecting to the mobile network. Basically it is stuck when fully booted. I can't go to settings to enable USB debugging or anything...

I am able to go to recovery and the bootloader and that is it..

Please help.. what do I need to do?