Ok, you have identified the source of the clicking, so lets work on what is drawing down your chassis battery.
The easiest thing to do is buy a DC clamp on ammeter. Amazon has them from Klein and Extech (two Chinese brands that have been around a while) for about $90.
Otherwise umplug shore power and check the chassis battery's voltage. It should be near 12.6. Then wait for about 4 hours and check it again. If it is lower than 12.5 then you have a fairly significant draw on the battery, more than something plugged into the cigarette lighter. Then see what could be drawing more than an amp or so of current.
David
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