spectro frozen analysers and CalcAxis motion filtering
In case a spectro has frozen analysers the GroupMove motions filtering leaves the IdentityCalcController even if there are no physical axes moving. This is due to the fact that IdentityCalcController.calc_to_real returns only the unfrozen axes which is a subset of all its reals.
Therefore in the motion filtering part (GroupMove.move) set(controller.reals) - excluded_axes
is not empty.