Hi there, since this commit: 584b822eb718550b9acb54f57744fd20bb0652ce, I get the following exception:
IllegalArgumentException: Material parameter is not defined: BackfaceShadows
It seems that the Material Definition Common/MatDefs/Light/PBRLighting.j3md does not define BackfaceShadows, thus the crash.
To reproduce this issue, you will have to set the mesh as a shadow receiver.