ARKit Environment Map trouble and solution.

This lovely error has given me trouble twice in recentmonths. All related to ARKit2.0’s  environment mapping. validateFunctionArguments:3514: failed assertion `Fragment Function(commonprofile_frag): incorrect type of texture (MTLTextureTypeCubeArray) bound at texture binding at index 4 (expect MTLTextureTypeCube) for u_radianceTexture[0].’ Environment mapping is