There are only 3 chances to lock the PERI to the gunners view or the Position it is in the Moment.
1) Switch to "Beobachten"
2) Switch to "Indexpos"
3) Override
If there is no Prob with your Key settings, the fault must be one of this.
In your first Picture, you are locked to "Indexpos"
So, this small Knob have 3 Positions, difficult to see, and you have to leave it in "12" position, then click in the Monitor. Thats how it works on my Machine.... ?