220V wire shielding

I have a board with leds that is driving a relay. When that relay is closing it’s contacts, is actually switching the 220V for the light bulb switch in my room. This board is quite long, like 50cm (half a meter). The relay is in the left corner, and the live wires from it goes in behind the board to the hole in the wall for the mains switch. I also have a mild steel sheet scotched to the board, and is for shielding, and I grounded it. But even If I have this grounded metal shield behind my board, the live wires are still affecting my entire circuit board, keeping it ON all the time. If I am disconecting the live wires from the relay, the board is functioning very well. Another IF, is if I disconnect the ground from the metal shield, the circuit goes nuts. So the shield is working fine, but only for the live wires inside the wall. The new relay live wires from its switch, are affecting again now.
I want a way to shield those wires.
Thank you !

IMO, if you need to ask, you may not be qualified working with mains.
In any case, this is not the best place to ask. Despite the name, we’re all about electric vehicles.