This last week we were camping at the beach, and I noticed a clicking sound when we were laying there at night. It didn't happen all of the time and I didn't feel like getting out of bed to figure it out even though it was driving me nuts. Finally one day it started when I was standing in the middle of the 'pod. It was coming from the fridge control panel. Click-click, click-click. With my experience with electronics I knew it was the sound of a relay clicking on and off. I also could hear the cooling fans in the exterior compartment running.
When the cooling fans turned off, the clicking went away. When they came on again, the clicking came back. 
Methinks its time for some more warranty work.