Just had this discussion at the dealer Thursday. According to service manager Harley will replace the gauges 1 time under warranty after that it is on you. He said best thing to do in his opinion is get a note in their file about the gauge. Then when Harley finds a fix they will replace the gauge. He stated some of the replacement gauges end up being worse than the one replaced. Somehow I smell a class action or full recall when/if Harley resolves the issue. Maybe that's why they haven't determined the fix yet after 2+ years.

 

I have had this issue in the past too, and I found that a few squirts at the vent holes under the speedo with a compressed air duster worked well. Worth a shot.