Paul from SWISCO responded:
January 29, 2016
Hello! It doesn't sound like an issue with the balances. I would check the window track to see if there is a kink in the frame that's rubbing the sash for the first inch or two. Sometimes the weatherseal hangs up in the sash and can cause a similar problem. Also check the interlock between the top and bottom sash for any dents that might be rubbing it. Finally, apply some silicone spray to the track and see if that helps.
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