Inverter transfer switch clicking repeatedly

An inverter's internal transfer switch clicking on and off repeatedly (audible relay clicking) usually means it's rapidly switching between shore/generator power and inverter power, often because the incoming power source is right at the edge of what the inverter considers acceptable voltage — flickering just above and below its threshold. Check the actual incoming voltage with a separate meter to see if it's genuinely unstable or if the inverter's thresholds need adjustment.