The DistanceToOut method of a G4Polycone returns a too big distance and then it crashes in G4VoxelNavigation::ComputeStep. You can find the description of the volume giving the problem at http://cmsdoc.cern.ch/~arce/oscar/g4-bad_polycone/geometry.lis I have added a printout in each DistanceXXX method of G4VCSGFaceted. You can see the output at http://cmsdoc.cern.ch/~arce/oscar/g4-bad_polycone/g4.out
The very helpful diagnostic output included in this problem report indicates that G4Polycone::DistanceToOut was invoked illegally with a position that is outside its boundaries. It is not clear why this happened, but it does not appear that a previous call to G4Polycone was the reason.
We could not reproduce the problem with the tests we have currently available and further investigations we could do. It would be extremely useful if you could provide us with a test case with a geometrical shape similar to the one used in your setup, so we can reproduce it. Thanks.