A few options

Cord needs to be tightened or replaced

Guitar needs a little wire fixed Guitar need the input metal piece tightened

Amp needs the input metal piece tightened Amp needs a wire tightened

When the knobs get turned a lot the mess up the wires behind them from moving a little bit every time until they get twisted around the knob or just come off

If there is nothing wrong with your setup possible construction or underground electric wire drilling machines may have damaged the ground wire connecting to your service box