PVM - Horizontal Bar using Scart

[amontre]

I recently got this PVM which i couldn't tell what model (no sticker at the back). It works perfectly when i connected my Wii using component.

But when i connected it using scart (via scart to bnc) to my megadrive or saturn, i got these faint horizontal bar moving up.

Am i missing something ? bad cable ?

[Anapan]

Looks like it could be interference from unshielded or not properly grounded cable, but hard to say. After verifying grounds throughout the system-to-display, possibly some capacitors would clean the signal?