Xbox RGB vertical lines problem

[TelaKeppi]

This has been driving me crazy lately. I've build several vga cables for my Xboxes and what ever method I use (sync splitter, SOG, internal sync), I end up getting these annoying vertical lines in the picture (see attachment). I have 3 Focus encoder Xboxes and I've tried them all, no difference. Same deal with 3 different monitors (all SOG capable). I get the lines only with RGB output, component HDTV out is clean, but it's not as crisp as VGA so I can't be 100% sure the lines aren't there. The lines are static on top of the picture and they don't move, they can be clearly seen on flat colored surface.

Unfortunately I dont have Conexant Xbox to rule out hardware revision fault. Is there anything hardwarewise I could do to maybe filter or clean the video signal?