That's a great idea, I should do it, but maybe the problem is not in the cable, as you wrote it is less likely to be with a printer cable and this one is from my old scanner.
I tried it with 2 different applications: LaserShowGen and LaserDock, and it was doing the same: one second it was showing a normal projection and the next second it was showing some inverted colors with miss aligned RGB lines, then back to normal, and that's how it was alternating every second.
The laser it self works perfectly with all its preset animations jumping to the music through its mic. When I connect just the ILDA (printer) cable it keeps working as it does without one, but when I connect the dongle to the other end of the cable turns into a dot that is pulsating, and when I connect the dongle to the computer the dot turns on/off every second.
So, I figured that it is not the programs, not the laser, but ... the cable??
These are the examples of what it shows:
What do you think it might be, the cable, the dongle, the laser ILDA input?