I have a 2007 DP which has been in a garage when not in use for most of its life. But this year it has been outside due to construction om a new garage. I have noticed that on the window on the driver...
I'm betting it's the seal and the water you're putting on the outside of the window is only making the fog on the inside go a way for a period. I had the same thing and could actually make it go away with the warmth of my hand depending on the temp. Took my RV to the Searcy location this past September and they did a great job at a reasonable price. Great people too with full hookups in their parking lot.