Tab 320S: Fixing window screen

californication

The driver side screen was always working very hard for us. After few months, I noticed that strings which control up/down movement "escaped" from side of the window, and they're freely "flowing". One part of the screen (top or bottom, I believe top) is moving uncontrollably, because the string which keeps it "synchronized" is not in place.

I tried fixing it several times already, by moving the string back between "clips" on the side of the window (unfortunately I don't have photos), but after few more uses, it goes back to the "broken state".

Does anyone know how to fix it permanently?