In order to see the effects of glitches in the BS oplev damping I requested that the servo be turned off for an hour yesterday.  
The attached figures show the effects of turning off the servo.
  
1) The spectrogram shows the relative change in the pitch, yaw and sum spectra when the servo is turned off at about 1900s and turned on again at about 5000s.
     1a) Note the low frequency kicks which both the pitch and yaw servos are introducing due to glitches in the laser power.  Stabilising the laser power may benefit this oplev.
 
2) The ASD plots show the change in the spectrum when the damping is turned off. 
     2a) The Yaw damping is good over a broad range of frequencies.
     2b) The pitch damping loop requires to be tuned further to reduce the servo bump between 2 - 6 Hz
     2c) The pitch loop also has slightly excess noise at low frequencies.