One of the problems could be the use of VertexNormalWS in a simplified way, which is to say, the vertex normals are not getting interpolated for more freedom of displacing the sand relative to the cliffs. Why is VertexNormalWS preferable to PixelNormalWS, which would apply that displacing to every pixel rather than basing it on the vertices of the landscape alone?
I agree with [USER=“3140864”]MostHost LA[/USER] that the Max node is limiting it or wrong to use somehow, and is probably part of how the sand is merely extended or contracted along XY horizontal and not yielding an optimal result, or is not flexible enough. It goes with what you were saying that the Max node takes each value of RGB separately and compares the sand to cliffs RGB values, then displaces the one maximum value of the two. That in itself is going to limit flexibility of the sand-adding mechanism.
Observation: There’s also a few holes occurring in the landscape in the video (to the left), which is probably geometry splitting due to the VertexNormalWS being ‘expanded’ or ‘contracted’ on the UVs.