I had the gauges on mine (2014) replaced twice under warranty - each time the problem immediately reappeared. I gave up then.
However, it's NOT condensation. Dealership took one of my sets apart to see. The inside of the glass has a coating of an oily substance, (presumably to prevent (!) condensation like the pre-Rushedmore bikes always had), and it's that that gets runs.
Interestingly I was in my dealer's workshop yesterday, and they were busy replacing a set on a 2017 FLHTKSE, which made me laugh. Discussing it with the tech, he says that they've had the usual "Harley knows of the problem, and is working on a fix" - which they seem to say about everything, replacing the older "They all do that, sir."
The problem can't be easily self-fixed either - the gauge rims are crimped on, and you have to pretty much destroy them to remove them, otherwise you could clean the gunk off the glass and solve it.