We have an ApexFP with two identical model screens connected via displayport.
Only the one set as the primary screen in monitor arrangement responds to the brightness control. The "internal" monitor brightness fader controls the monitor set as primary as well as the encoder touchscreen. The "external" monitor brightness fader does nothing.
I have tried swapping which monitor is set as the primary and the result is the same, only the primary one can be controlled. This proves that they both can be controlled.
Maybe this is an issue with the FP because it has no built in primary screen?
EOS version 3.3.4
Tim.