World Position Node Breaks Baked Lighting In Masked Materials

Baked shadows don't seem to work properly when Absolute World Position is involved with masked materials. The masked material won't render a shadow at all in this case.

1. Open attached project
2. Open material applied to cube mesh in the scene
3. Change the scalar param "height" value to .1 and compile
4. Build Lighting

RESULT
The shadow disappears completely.

EXPECTED
Half of the cube mesh's shadow is projected since the rest is masked.