Digital input nose from wires Please Help!

Hello, I have the arduino uno installed to control one room lighting. There are two main loads, each switched by its ssr. One is a regular bulb, and the second is an switching supply (possible cause of noise?), which provide power to an rgb strip. The strip is also dimmed on each color with transistors and pwm.

Everything works fine if leave the input for the two buttons unplugged and simulate the button press with a wire. If I connect the actual wiring (running in the walls with mains - no other choices...) works fine, but once the switching psu is turned on I get phantom button press and lights go crazy until the switching psu is off again.

Debouncing is done by software, and is working fine. I can't work anymore on this otherwise I won't be able to normally switch the lights. Pull ups are enabled internally. Also tried with 4.8k and 3.8k external pull ups, no improvements at all.

I don't have a small ceramic cap to try as I read suggested on the forum, but will this make al that difference?

Please, I need some suggestion...

Capacitor may work but how long is the switch wire? It may need to be shielded or use twisted wire.

Weedpharma

I don't have a small ceramic cap to try as I read suggested on the forum, but will this make al that difference?

I'm quite sure it will. Here's a circuit suggestion where the 1K will protect the cap from being directly shorted by the switch and it will also help to dampen the noise. In this case, the capacitor need not be ceramic type: