Check that a plate is aligned with an axis

gprMax/user_objects/cmds_geometry/plate.py

@@ -96,6 +96,7 @@ class Plate(RotatableMixin, GeometryUserObject):
             (xs == xf and (ys == yf or zs == zf))
             or (ys == yf and (xs == xf or zs == zf))
             or (zs == zf and (xs == xf or ys == yf))
+            or (xs != xf and ys != yf and zs != zf)
         ):
             logger.exception(f"{self.__str__()} the plate is not specified correctly")
             raise ValueError