I have bumped into a strange issue: In the physical world, I have a voxel grid (implemented with a G4VNestedParameterisation) with a G4VSensitiveDetector attached to it. Adding a parallel world containing a voxel grid which exactly matches the physical world voxel grid causes the G4VSensitiveDetector to give wrong results. Offsetting the parallel world voxel grid a bit fixes the problem.
Is this a known issue? Does the navigator get confused because of that?