The only frost or condensation build-up that happens in my fridge (same year and model TT as Ronny's) is on the aluminum fins inside the unit in the fridge section. There is a small plastic catch basin below them, and it drains directly to the little pipe being discussed here.
Like Henry, ours really only dribbles after shutting the unit off. We tend to get a small buildup of ice/water on the fins over one or two weeks useage, especially during humid periods of weather. Not enough to block the fins, but there is a buildup.
Even though there is "filter" designed to keep critters out of that pipe, I'd recommend making sure that it isn't blocked. Pour a bit of water in the catch basin and see if it dribbles out where you'd like it to go.
Remember that the main fresh water tank, pump, fills for both city water and fresh water tank, fresh water tank drain, bathroom sink and toilet, and piping in between are all on that side of this model within a couple feet of the fridge. There are plenty of other sources of water leakage there.
The only penetrations of the belly membrane under the fridge are: the propane line to the fridge, wiring, and hard ground line. There are no factory installed drain points on mine, either.
One other possibility. The shore line door is directly under the fridge. As we all know, the opening for the shore line is much larger than the cable itself. If water gets in that door, it drops immediately to the floor of the trailer, and would seek the first opening in the floor it finds. That may well be the propane line or the wiring since they are within inches of other. That could well account for wet insulation there.
It is an easy check, open the door and reach in there. There are no exposed wires, just wooden walls, floor, and shore line. If the floor is wet, it doesn't necessarily prove that the water is coming from the shore line door, but it does narrow the search. Also check the walls and ceiling in that compartment for moisture. If they're wet, then the source is likely not the door.
My fix for that shoreline door is to place a short section of pipe insulation on the cable, and wrap with some electric tape to keep it on the cable. It can slide on the cable but won't come off. Just center it in the opening and make sure the cable and insulation dangle down.
Also, remove the drawers under the pantry and see if there is any moisture there, too. The city water hookup comes in there and could easily be a source of moisture.
Dan 
Linear Mode
