I experienced the same thing as Buzzzzz. Playing around to get familiar with the node network, I came up with a file, that consists of a Heightfield generated terrain, a Heightfield load terrain and a terrain made from a power fractal. When I insert a shader clip file, the terrain(s?) disappear. I could solve the problem by 1. generating the heightfield again after inserting the shader clip file, and 2. after that unchecking and checking the read from file button at the Heightfield load terrain.
I have included the tgd file, the clip file and the heightfield load terrrain.