Constant DERIVED_GAINS_MESSAGE 

pub const DERIVED_GAINS_MESSAGE: &str = "franka target control: this session has no live tuning; \
     its Cartesian gains are not a scaled ImpedanceGains::CARTESIAN, which is all the one \
     tunable stiffness can rebuild.";

The message of the FrankaError::InvalidOperation a live-tuning call returns on a Cartesian impedance session whose gains LiveTuning::gains cannot rebuild from one Cartesian stiffness – ImpedanceGains::DROID is the preset this is true of. Such a session keeps the gains it was started with and is given no tuning slot, rather than having the six derived dampings rewritten in one cycle by the first change to any other field.