markus_ll , Most likely it is a problem firmware. 8.0 March patch. I and many other 8.1 has not yet come, and will come not soon. As for Sberbank, on 4pda it is patched.
Android Oreo 8.1 ver.00WW_5_580to install through recovery TWRP. Please check the installation of firmware. Pre do not forget to make a backup. Download
who can write a completely manual receipt Ruth rights which program download can be necessary for a reference, except the adb, can be useful to someone or I'm alone when I was a noob here, for the first time in such a situation at MTC was easier to get Ruth.