Yes, I understood that and agree with you that at these high frequencies usually coaxial cables should be used. I only use shielded cables, though. But I think it works just fine.
I thought you talked about external radio signals interfering with my control signals.
All cables in my electric cabinet are arranged in a way that signal and power cables are spatially divided from one another. I did the best I could for avoiding interferences and I think it's sufficient. I mean, I don't have any real disturbances or unpredictable movements. They always happen at the same code lines and all motors behave like that, the dual axis even synchronously. If they would be out of phase, the portal would change its orientation on the linear rails by little. But I let the Gcode run several times now and measured all angles between my axes afterwards. They didn't change a bit.
It get's a lot better though by increasing the speed and playing with different accelerations.
I don't there's a fast solution now, it's probably something that has to be worked out step by step. It could be everything. Next step is that I'll update my CAD/CAM solution the next days. I see a good chance that this could vanish this weird movement as Autodesk did some severe changes to their software.
I'll take note of every change I make on my machine in the future and check if anything has changed regarding this. If so, I'll let you know.
I want to thank you, Craig, for your time and your willingness to help. I really appreciate it, many thanks!