The blending mode dropdown lists, for both layers and brushes, usually closes before I can make a selection. Sometimes I can't even scroll down. It often takes several tries before I can hit it just right
I don’t remember exactly, but I’ve been using screen size canvases and no more than 3 or 4 layers. Pixels and probably watercolor and/or oils. The problem was universal throughout the app. After plaguing me for a day or two, it seems to have cleared up now.