Hello there

From file "MODULE:G4SPSPosDistribution.cc" body of the function GenerateRotationMatrices() on row 186 in package geant4_9_5_p01 and in geant4_9_3_p02 down to maybe
"
...
  // This takes in 2 vectors, x' and one in the plane x'-y',
  // and from these takes a cross product to calculate z'.
  // Then a cross product is taken between x' and z' to give
  // y'.
  Rotx = Rotx.unit(); // x'
  Roty = Roty.unit(); // vector in x'y' plane
  Rotz = Rotx.cross(Roty); // z'
  Roty = Rotz.cross(Rotx); // y'
...
"
(Rotx,Roty,Rotz) form matrix transform and then used. But obviously is not orthogonal. It must have, and I add this:
Rotz = Rotz.unit();
Roty = Roty.unit();

I'll email author Dr. Fan Lei to let him know too.

Bye there