Electrical gremlin all electrics pulsing/ flashing.

Not new to navaras having issues my previous 2007 had plenty over the years. I bought 2013 navara and it developed a problem (there's a surprise 🤦) so in general it runs fine but after a short amount of time when idling it starts pulsating (front n rear lights, dash, radio etc.) We have changed the battery and alternator checked for loose earth cables (none visible) scanned it when it was doing it and no fault codes. Checked the battery and alternator when it was doing its thing and seemed fine. Question is does anyone know what it could possibly be? I have tried searching for answers and failed spectacularly.