Xiaomi Mi Box – HDCP 2.2 Probleme AV-Receiver after Nougat update

Hello everybody,
After a long weighing up, I have my YaVDR client retired and on recommendation of the Kodi forum bought a Xiaomi Mi Box.

Config:
Xiaomi Mi Box 3s International Version
LG LED 1080 (of course without HDCP 2.2)
Denon AV Receiver AVR-X1400H

With Android 6.0 everything was fine. Since I would like ATMOS and my TV picture (yaVDR-Sever VNSI-Addon) was a little jerky, I’ve updated to 7.0.

Problem: Sound works but no picture (no android user interface) – receiver announces that my TV got no DHCP 2.2 support and therefore is not transmitted.
Directly at the HDMI of the TV it works.

Did someone had the same problem?