Sash Channel Balance binding at the bottom

A quick learner says:
S385-27 : 27" Series 385 Channel Balance
option: 2630

The window weights 18.4 lbs

I've recently purchase 2 of these Channel Balance and installed both to replace to ones I have on the window.

After I pushed the window down into the closed position, the window sticks very badly when I try to lift it up. When I replace just one of the new SWISCO channel balances with one of the original ones, the window can operate fine with very minimal stickiness; however, it is still slightly sticking in spots.

Any idea what could be causing this ?
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Tom from SWISCO responded:
Hmm... I'm not sure. Can you confirm that you have the Series 385 channel balance? How well do the nylon attachments match your old ones? The Series 385 uses our 19-005 top and 15-004 bottom. Carefully examine the specs we show for them and if they differ in any way from your old parts, let me know how and we can work from there.
A quick learner says:
Hi Tom,

thanks for looking at this.

I've attached some photos. In all 5 photos, the bottom one is the old-original channel balance; the top one is the new SWISCO channel balance that I've received for the order.
User submitted photos of a window balance.
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Paul from SWISCO responded:
Hmm... I'm at a loss as to why it's not working. Maybe try spraying the tracks with silicone and see if that helps. In the meantime, what was the number on the original balance?
A quick learner says:
it doesn't have any stamping as far as I could tell - it's original when we moved in - quite some time ago - more than 10 years.

I'll try cleaning the track and applying some Silicon spray. Thank you.
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