In my first playing with blending, I had a strange issue. Some paint will blend, and others will not. In the attached example, the blue and tan mix, but the red only does sometimes. There is one area near the middle that almost never blends. You can blend from somewhere else over it, but you cannot START a blend from that area. By blend, I mean the new feature where the oil brush has a loading of zero.
I have the painting file if you want it.
I also get the error... success message box, by the way.