my answers are following your questions.
-Is the content on both displays always the same?
No! When I turn the Knob 1 the left display show its information properly, however when I turn Knob 2 both displays show Knob 2 info. And so on…
-Is the content normal at first, but does it become the same on both displays after you turn knob 2?
-Is the problem only occuring with knob 2, or also with knob 1?
Just Knob 2
-If you assign something to knob 1 and knob 2, then turn knob 2 to create the problem case, and then turn knob 1, is the right content shown again?
Yes. My test: input1 connected to GXHogsFoot / Boost linked with Knob 1 / Mix linked with Knob 2 - When I turn Knob 1 the left display shows boost info / Them I turn knob 2 and both displays show Mix info / Them I turn Knob 1 again and left display shows Boost and right display shows Mix.