I noticed a couple of minutes ago that IMC-F and a few other arm length channels briefly had a very low frequency oscillation with a period of about 2 minutes. This is the period of the BRSs so, I did a quick check and found that BRS-X was damping at the time. Attached trend shows a BRSX velocity montior, IMC-F_OUT and a couple damping status bits from BRS-X. You can see from the BRS velocity that it was a little rung up, the damper engaged as designed and quickly brought it back down, but when the damper engaged this coupled into some of the IFO length signals. A couple things to prevent this would be more low frequency roll off in the sensor correction filter, or revisiting the thresholds on the damper. This is all at 8mhz though, so maybe it's not such a big deal.