Illustrator suddenly automatically changes my artwork fill color to white #fff
Very frequently, if I am working on several .AI files at the same time, when I switch between the files' tabs, artwork for one of the layers in that .AI file I switch to will suddenly have a white fill.
Here's how it usually goes.
1) Have multiple AI files open.
2) switch to one AI file.
3) switch back to another AI file, and the layer that was most recently selected will suddenly have an #FFFFFF fill. I can click "undo" to get back to the correct fill color, but it takes about 3 or 4 undos to get back.
Sometimes it will happen to random layers as soon as I open an AI in Illustrator.
I've not found anyone else with this issue. Any suggestions are welcome! It's very frustrating.