I have an Andersen window that I installed 21 years ago and one of my sashes is bad I was calling around to get prices and one glass company said that it didn't sound like a broken seal as there is no fogging in the middle. I called Andersen and explained what was happening and they thought it was the sash frame was bad but it was out of warranty by a year I explained that this has been going on for some time but it has gotten worse. The CS lady said she would check with her supervisor and let me know what to do. She came back and said they where sending out a new sash free. Now I think that is great customer service.