I recaulked the wide gap in the exterior fridge compartment. After doing that, I rechecked the caulking at the bottom of the camper side panel. Saw some discoloration in an area about 4" long. When I pressed the panel, it separated from the bottom trim. Resealed it. I think this area is much more likely to be the problem, as rain would definitely get directly on it (vs passing through the louvers of the fridge compartment to the large gap).
Also, as recommended here, I ran a small electric heater for a while inside the interior compartment. Most of the discoloration on the wood panel (evident in the original picture) disappeared.
The next rain will tell if I really found the problem. :)
Thanks for the suggestions.
Ralph