Pella Double Hung Windows from 1989

We built our home in 1989 and have a lot of Pella double hung windows. For several years now the weather seal on the inner glass panel (tan in color) sticks terribly when trying to take them apart to clean. We've tried wiping on a few different products, but nothing prevents it. When I called Pella to ask about replacement seals, the rep told me she couldn't answer my question, I would need to pay for a service tech to come to the house and look at the windows, then he could tell me if seals are available. I'm not about to pay $100 to have a guy come here when we have no idea if the seals are even available. Anyone have any knowledge/experience with these seals?