Consolised One slot problems

I have a consolised MVS one slot but am having some sound issues. Whenever music is playing distorted lines appear on the screen. If I wiggle the lead around they do disappear but I end up with a load buzzing noise that can be heard underneath the music.

Does anyone know what the problem would be. I've been told it could be that my scart lead isn't grounded, but I don't want to spend money on one if it doesn't fix the problem.

Your audio output is likely sharing a ground with the video output or as you say the SCART isn't grounded itself. This causes interference in the video lines. Try unplugging the audio and looking at the video. If it clears up, it's a shared-ground issue. If the image disappears, it's a non-grounded SCART issue. What happens in the case of a non-grounded video line is that it grounds through the audio, causing the interference.

Is it the scart lead that I have to open up?

Also it's a scart to scart lead, is that a problem?