During today's lock we have seen a high narrow peak at 46.1 Hz. This looks to be separate from the wandering 48Hz line (seen as a lump in our DARM spectra).
Bottom plot of attached screenshot is a 0.01 Hz resolution DARM spectrum. The top plot is zoomed into the 46 Hz region: black is a reference from Feb 28, grey and yellow are from two points during today's lock, with low and high ~48Hz line activity respectively. The 46 Hz line was also present in our Feb 28, but today it is a factor of ~4 larger for sone reason.
I ran bruco for a quiet time during this lock, but didn't see strong coherence with anything (closest being 0.21 coherence at 46 Hz with LSC-REFL_A_RF45_I_ERR_DQ).
(I had run bruco at a different time, and was excited to see coherence with an end-x sus rack magnetometer, but it turns out there was a glitch in the time window I picked.)
This feels reminiscent of the Hartmann wavefront sensor camera refresh rate. Team TCS is going to look at this as soon as they are finished with their currently-ongoing maintenance tasks.
EDIT: Never mind, Danny looked, and all of the refresh rates are correctly set to be much lower frequency than this.