This is just comments for used channels about safe/unsafe issue. 

[K1:LSC-AS_PDA1_RF17_Q_ERR_DQ]
The reason why violin mode peaks are also mitigated seems to be to use AS17Q. AS17Q is DARM signal with poorer senstivitity than DCPD. So high-SNR DARM motion such as violin mode peaks can be seen also on AS17Q. So AS17Q and calibrated DARM should have large coherence in the frequency band in that AS17Q is not limited by the sensor noise as shown in Fig.1. Even if poor SNR, coherent signal can be seen on AS17Q with long enough integration time. For this reason, AS17Q might have to be regarded as unsafe channel.

[K1:PEM-MAG_BOOTH_EXC_{X,Y,Z}_OUT_DQ]
I recall that around the time of O3GK, Washimi-kun or Yokozawa-san pointed out the possibility of seeing the DARM signal on the magnet meter via change in the magnet field by the coil magnet actuator. So I checked magnet meter signal during the Pcal injection for the calibration measurements. Then we can see the moving coherence following pcal swept sine Fig.2-4. My check is just a very short integration time but it suggests possibility a coupling from DARM to Magnet meters (Note that for the fair evaluation, same check had better to be done when DARM is controlled by ETMY). So we should check magnet meter signals are really safe or unsafe to use removal works.