The problem is that the inverters are set to search mode, and are looking for a load that is high enough to turn them on. It does this by sending out a small current to determine if anyone wants to consume it. The search load is adjustable.
Download the manuals from xantrex web site and go through them to learn how to operate the inverter menu system. You can set the search wattage up to keep it from clicking on and off.
I recently dropped my bus off at the shop to have the oil changed. Before I left, I set the inverter to search. The fridge was the only thing on, and it was running at the time. When I went to pick it up, the carbon monoxide detector was laying on the seat. I plugged it in and it started beeping every second. Yep, the inverter was in search mode and every time it would search, it would cause the CO detector to beep like it does when it's plugged in. Good think it was in an area that is not heavily populated. I'm sure the mechanics were wondering what the heck was going on when they got to work the next morning.