I had the same thing, the converter is likely going bad. Eventually the lights will go dim and not get bright again. If you can get to the converter it is an easy exchange to take out the old and put in the new. Mine had 4 screws holding it to the floor and two big set screws holding the heavy wires coming from the fuse box. Took 5 minutes to replace.
In the mean time find your converter and get a picture of the data plate so you know what you need to buy to replace it. If you want to chance not ordering one until it fails at the very least you will want to carry a small battery charger with you. An important thing to remember is that even though your refrigerator runs on AC power when you are hooked up at the campground, the control board telling it to run is 12 volt. If the converter dies and your battery then also dies, your fridge will not work.