Landscape painting issues

I am having no luck using the landscape features in UE4. Whenever I paint the heightmap or landscape textures I get black blocks and other artifacts that do not go away after rebuilding lighting. Also, the cursor appears under the terrain and the whole process is quite buggy and not usable at all. (Sometimes the terrain heights will just not adjust, sometimes the painting has no effect at all). I am using UE 4.7.3. I have tried building the most basic materials, using starter content materials and I am now using the advanced display landscape materials from the market place and I am quite stuck at this point. Any help here?

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Adjust the brush radius to something really big, paint whole your landscape with only 1 layer. then start painting whatever you want. You should no longer see the artifacts.

I have done that, but after adjusting heights again I get the black areas again. I can’t repaint the whole landscape every time I make a height change. Also, when I rebuild the lighting it is always missing shadows (Like no shadows at all) but if I change the static lighting resolution in the landscape properties it looks just how I want it to look. Am I missing something?