I''ll often add the CC Vignette effect to an imported .AI layer to help it blend into the scene. It's very helpful in not adding additional clutter to compositions, but it increasingly makes scenes go crazy. Different zoom levels will exacerbate the bug, and saving and reopening with the effect applied seems to make it worse.

Some of the symptoms include weird screen tearing, little dots all over the comp, and the layer will "flicker" on and off as well as affecting the alpha channels on other layers.

I've attached a quick sample. This mostly shows everything but the tearing.