LeEco Max2 (x820) - SmartLock Face Recognition not working

Hint: my phones language is set to german so i translated the menu items etc. to english.

Bug description:
If i try to activate “Settings -> Security -> SmartLock -> Face Recognition” i cannot do because it says “The camera is not available”. (The original Google camera and also Open Camera works pretty well for taking photos)

Affected version: MK81.0-x2-201806031522-NIGHTLY
(Build Number: mk_x2-userdebug 8.1.0 OPM2.171019.029.B1