The MICH and PRCL motions have been measured in some different configurations.
According to the measurements :
+ PRCL is always noisier than MICH.
+ MICH motion becomes noisier when the configuration is Power-Recycled Michelson (PRMI).
The next actions are :
+ check the ASPD
+ check the demodulation phases
+ try different RFPDs to lock MICH