added IO error in case mixed BC that allow rotation are given

code/DAMASK_spectral.f90

@@ -254,6 +254,9 @@ program DAMASK_spectral
      print '(a)', 'drop guessing along trajectory'
    if (any(bc_mask(:,:,1,loadcase) .eqv. bc_mask(:,:,2,loadcase)))&                ! exclusive or masking only
      call IO_error(31,loadcase)
+   if (any(bc_mask(1:3,1:3,2,loadcase).and.transpose(bc_mask(1:3,1:3,2,loadcase)).and.&
+           reshape((/.false.,.true.,.true.,.true.,.false.,.true.,.true.,.true.,.false./),(/3,3/))))&
+     call IO_error(38,loadcase)
    if (velGradApplied(loadcase)) then
      do j = 1, 3
        if (any(bc_mask(j,:,1,loadcase) .eqv. .true.) .and.&

code/IO.f90

@@ -1198,6 +1198,8 @@ endfunction
    msg = 'non-positive result frequency in spectral loadcase'
  case (37)
    msg = 'incomplete loadcase'
+ case (38)
+   msg = 'mixed boundary conditions allow rotation'
  case (40)
    msg = 'path rectification error'
  case (41)