Problems with Material Layering

Hello… I’m working on a static mesh terrain, attempting to use the “splatting” method of layering and masking for variation in texture and to break up tiling. Now…

For two layers, I have what might turn out to be a working terrain texture, but I’d really like at least two more layers over the base two.

Unfortunately, when I bring in my third material layer blend instance into the layered material instance, it wipes out all textures from my terrain. All of the checkboxes are on, I have a mask for this third layer, and its eyeball icon is checked on. However, I’m only seeing the default, pixelated material on my static mesh terrain. When I turn the third layer’s eyeball icon off, the lower two layers reappear.

Any ideas??