I took at look at the 3.5hr lock earlier today (1231211560 - 1231224532) and do not find evidence of scattering in GDS-CALIB_STRAIN which had been present in locks prior to the DARM actuation being moved entirely to ETMX. 

I do however see whistles (the last time we saw these was back in October); hveto finds them dominating in rounds 1 and 2. Looking at individual whistles they can be seen in SRCL_IN1, SRCL_OUT, POP_A_RF45_I, POP_A_RF9_Q, REFL_A_RF45_I, REFL_A_RF9_Q and REFL_B_RF45_I/Q_YAW. We usually blame something beating with the IMC VCO for whistles, so I took all the trigger times from hveto's round 1 and 2 winners and found the IMC VCO frequency at these times. Note, not all the triggers will be whistles, but the majority will be. The attached histogram shows the IMC VCO frequencies at the time of the whistles. I also took a look at the ALS_COMM and DIFF VCOs at these times and found they were not changing at the time of the whistles.

I also took a look at the IMC VCO frequency ranges for the last few locks, just to see if it had shifted significantly. It has not. Since 10th Jan the IMC VCO frequency has been centred ~78.96MHz, but whistles only appeared in the last lock....