So does anybody have a tested guide to update an N950 to PR1.3 without completly bricking it?

I tried the N9 repo way and I got an N950 that auto uninstalls every deb package it could find. Even the lockscreen was uninstalled after some minutes.
After reflashing PR1.2 I had a working system but I can't use my SIM card because anything fails everytime I try to flash PR1.2 again. No no mobile internet connect, messages or telephone functions.