#1 is likely your problem. SWGs can easily scale if the CSI (calcium saturation index) gets too high. You are better off with a slightly negative CSI to keep the scale off. You can use the poolcalculator.com to figure out your current CSI.

Also as cells age, then tend to accumulate more scale. I would avoid scraping the scale since that could also scrape the cell coatings. You are much better off using acid to clean cell then any mechanical method.