I'm having issues masking in my cracks using a simple mask. I'm not sure if it's the small ~0.2 scale of the cracks or what but the colour map, comes through with spots in the render, and the spots can be seen in the 2D preview of the layer mask, but are not present in the colour map PFs. Additionally, the crack floor colours vanishes all together in the Surface Layer while it's broken up all over the surface layer. Even more interestingly, the cracks map seems to work fine for the crack floor displacement mask. Seems to be an issue inside the surface layer.
There are no settings on the surface layer, breakup is turned off, and just colour set to 1. The colour mask map created from the scalar is solid, shows no breakup, and is clamped.