My GSA Isolator silkscreening is still perfect, and I use it, so, I would think someone's fingers are dragging over the screening.
My Urei mixers silkscreening is also perfect, and when I worked in clubs, the clubs mixers also had worn away screening. Fingers are pretrty much always the culprit.
The system your GSA is in? Is this a system you rent out? IF SO, operator error.
Mr. Scott Fitlin