I have been making wine for almost 50 years and never had this happen.

I have six gallons of blueberry wine that has been fermenting for about nine
months. It stopped after about four or five months and appeared to be
finished.

About a two months ago, I added 1 1/2 teaspoons of Potassium Sorbate and 2
teaspoons of Potassium Metabisulfite to get ready to bottle. It started
working and is slowly bubbling away. It tastes dry and quite good.

I had a refractometer brix reading of approximately 3 when I added the
Potassium salts. Our local winery owner told me that a few other people had
the same thing happen to them. Is it possible that the Sorbate or
Metabisulfite may act as a yeast nutrient of some sort?

Does anyone have any ideas or suggestions? I want to bottle it.