This occurs when using 3D source objects. A 3D source object doesn’t have a material specification so it gets its material from the object that encloses it. This warning occurs if there are multiple objects enclosing/intersecting the 3D source object. In this case, the 3D source object is assigned the material of the last object that encloses/intersects it, and this might not be the intention of the user. If the enclosing/intersecting material properties are the same, there’s no issue. To avoid material inheritance issues, a workaround is to use a 3D block object with specified power (and intended material property), in place of the 3D source object.