Now , as the software more or less does what I need, I'm now facing a much more severe problem at the receiver side.
(I tested with a 3 channel receiver, so only 3 servos max used)
The servos, that are driven from a slider don't stay calm but are really noisy.
They jump in a timely random manner around three times per second into the shorter puls direction (The end of the servo horn moves about 2mm, sometimes even more).
with rare exceptions, all three servos jump at the same time. I would say at 90% of the time, all three servos jump at the same time and now and then anyone of the three makes either an extra cycle or misses one.
On the system screens and in DIAGANA menu, Channel bar and/or number displays do not show any recognizable variations.
Servos driven by the pots that are connected to the identical voltages (+5v and ground) as the sliders, stay absolutely calm at the same time.
When I hardcoded a fix analog value for all the channels (instead of measuring) the servos stayed still, no noise.
I permanently have added capacitors (0.1uF) to the slider signal wires (= inputs to the multiplexer).
I tried several delays between selection of the multiplexer and analog measuring
I tried (up to 10) dummy measuring cycles before the actual conversion cycles
I added/removed switching the selection lines of the multiplexer from outputs to "inputs with pullups" at the end of the routine
None of the above changed the behaviour in a recognizable manner.