The following printout is occasionally triggered in complex setups:

*** G4Exception : GeomNav0003 issued by G4VoxelNavigation::ComputeSafety()
   Safety method called for location outside current Volume.
Location for safety is Outside this volume.
The approximate distance to the solid (safety from outside) is: 0.000473851
 Problem occurred with physical volume:  Name: XXX Copy No: Y
   Local Point = (X,Y,Z)
 Description of solid:
     :

due to additional debug checks activated by default in the code of GG4VoxelNavigation::ComputeSafety(), which should be instead be protected between G4DEBUG_NAVIGATION flag.