Are we using high-quality cables, guys?
You'll get ghosting and interference if the RGB cable is made of doorbell wire.
When I set my STe up recently, I decided to make my own RGB cable to connect it to either my Commodore 1084S, or the Philips CM8833-MkII. All I had, cable-wise, was a piece of overall-screened multicore wire. In other words, the individual wires weren't screened from each other
(this is the important part) - just all screened as a whole from the outside world.[In case I'm not understood here (sorry if I'm being confusing! ), "screening" is the braided hair-like wire, sometimes coupled with a tin foil-like material, that's wrapped around the wire and shields it from interference.]
It worked, the picture was stable and sharp, but there was ghosting, especially on highly contrasting colours, and text etc. I also had some strange interference from the floppy drive motor; when the drive was accessing a disk, the screen would get some rippley interference - not nice!
So, later on I was given a spare VGA cable, a very thick one. Thick cable is a good clue to the cores being individually screened from each other. Chopped the ends off, found four individually screened cores; one for each colour, and a nice screened sync, too, the few remaining wires left for monitor data and extra sync signals in its original VGA application. Stripped the wires down, twisted all the screens together and soldered them to the plug connectors' bodies at both the D-sub and 13-pin DIN ends, and connected up each line. I used a few resistors to suppress the color signals down a bit as recommended in a few guides for making 1084S/RGB cables.
Ghosting's practically gone, picture is lovely.
No more floppy interference either - so the crosstalk between color signals is eliminated.
However, I do get some very minor interference, not just on the screen but also on the audio. I have a feeling that it might be remedied when I get around to re-capping my power supply, which I hope to do soon. I think the power supply has a part to play in suppressing noise, so when it's capacitors are old and dry, it cant work as well to supply a good clean signal. A while ago I was probing the power supply with an oscilloscope and found the same interference I was getting on the audio outputs inside the PSU too, so hopefully a good service with new caps and other components should sharpen the machine right up.
Just some of my experiences... I hope you manage to find a remedy, dude.
Stuff like this does annoy me too, and takes away from the enjoyment of these old machines.