Now i have tried all of the above suggested solutions except the red cut-off which I will do later, my first priority is to solve the phantom lines.
When I reduced the screen size using both the pot inside the arcade and the settings for resolution in mame I got rid of the phantom lines at the top of the screen.
But there are still phantom lines near the bottom of the screen, and these are always running all the way across the screen. These are the same ones that I mention showing up for only a second during boot, when going from dos->windows.
I tried shrinking the display (with the pots) to a very small vertical size just to see if they would go away as the ones in the top did, but they just followed the screen along.
I've tested a bunch of games and I found one game that with specific settings didn't show any of these phantom lines and it was Ghost 'n Goblins. What I did was that I removed the "Stretch Using Hardware" setting in Mame. The reason this seems to work in Ghost 'n Goblins only and no other games that I've tested so far is that GNG's hz is H60 and not V60 as the rest.
Does anyone have any clue to what may be causing this? It seems as if as soon as the Vertical sync is involved it messes up

Btw: Enabling "triple buffering" didn't give me any change in the picture whatsoever.
I also included a picture of the inside of my arcade, showing where I soldered the ground from the RGB wire. I'd like to know if this is a suitable spot to do this?