Second HDX screen doesn't show the transponder info on the topbar anymore

[MarcF]

Sinec a while my second HDX screen doesn't show the transponder info on the topbar anymore.
Formerly I could use both screens to work with the transponder or check the squat, now it is only possible on the primary screen.
What went wrong?

 

[Dynon]

It's connected serially to each display, so most likely that connection has been severed.