Hope you are all well

This one maybe for the technical and service type gurus amongst you...
Got a Barcrest Horizon cab and the audio picks up interference from the lighting circuit.
Not all the time but certainly when there is a lot of lights on (especially in attract mode). And it is bloomin' annoying...
Now I did read somewhere it could be a psu issue - so swapped the psu with a known good one and the same thing happens...
The previous owner of the machine has gaffer taped the audio cable loom to the wiring loom for the coin mech - could this be the problem? Bit daft to do this if you ask me....
But I am daft and that's why I am asking your expertise!
Hope some marvellously talented expert can help me.
Thank you in advance and have a nice evening...