Hello Leenhoef,
First o fall thanks for reaching out and using our products

This sounds like Cuelux is receiving short unwanted MIDI commands from the Midicon.
Because you are using Fader Start, even a small unexpected value from a fader or flash button can briefly trigger a playback. That would explain why other cues flash for a moment and why the Go button turns orange.
Please first try disconnecting the Midicon, restart Cuelux, and run the same cues with the mouse only. If the problem stops, the issue is most likely coming from the MIDI controller or MIDI setup.
Also check `Options > MIDI` and make sure the correct Midicon input and MIDI map are selected. You can also temporarily disable Fader Start on the affected playbacks to see if the random flashing stops.
If the cues are different looks for the same fixtures, it can also help to put those playbacks in the same Bundle, so they release each other instead of running together.
Hope this helps!