It was stupid me. I have a Roland PC 180 which has one slider.
Normally you control the volume with it.
But if you change it,pressing MIDI-Button, one key, you can change it to send f.e. Aftertouch messages.
I mussed have changed it, when i intended to change the midi channel…started playing without pressing the Midi-Button again.
When i will be testing the program change later, it will be a journey. I have to press 6 keys iirc.
The later trace worked. the CC7 volume in the zynthian screen was changed!?