I have two Gamecube digital-to-analog converter cables that are modified for RGBHV output with VGA connectors. One of them was done by a company, the second one I did following this tutorial somewhat: http://gamesx.com/wiki/doku.php?id=av:rgb_mod&s[]=vga

Both of these cables do not have proper R/G/B return / ground. Instead, only the outer shield and the sync ground are wired correctly.
On all CRT monitors, my VGA capture card (PEXHDCAP) and one old LCD monitor (that doesnít have any inputs beside VGA), the picture is perfect with no blurring or any other problems.

However, on newer LCD monitors, there are slight vertical lines running down on the entire screen. They are stationary and always the same. It looks like every second pixel was slightly darker than the first.

Now I believe that this is because not all wires have separate ground. On the cable I modified, I tried to solder all of the 5 grounds (R, G, B, sync, shield) to the cable, but I had to decide against it because they were slightly shorter than the others, so all the strain was on them and the solder points kept breaking apart.

My main question is whether the problem on some (newer?) LCD monitors is because these require separate sync, or if they simply arenít tuned for displaying VGA signals correctly any longer.
In other words, if I re-solder the cables and connect all separate grounds, will the picture be fine on all new LCD monitors? (Iím sure the monitor isnít faulty because there are no such artifacts when using DVI-D.)

Also, in-depth knowledge about VGA signals and especially its grounds / returns is very much appreciated!
I did a Google search, but the best post I could find said that separate sync is important so that there is no interference to, for example, red from green return, which would cause color blurring.
If that was the problem, I would expect the problem to appear on all monitors, and not only on newer LCDs. So Iím not really happy with that explanation.