I ran my (now 3x faster) BruCo script using a lock stretch that Dan pointed to me, from last Friday (GPS time 1107840506 + 600 s). The report can be found at the following address:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1107840506/

Here is an excerpt, but yuo should definitely read the whole book:

• The low frequency part (below 20 Hz) has good coherence with angular WFS at the AS port, as well with the power at the AS port before the OMC. I suspect this indicates that the noise is due to some angular control. If I'm not mistaken, the DHARD loop was on at that time.
• Coherence with the auxiliary degrees of freedom is quite high everywhere: in the ~10 to ~300 Hz with MICH, pratically everywhere (10 to 2000 Hz) with PRCL and SRCL.
• Between 200 and 400 Hz a couple of bumps (280 Hz and 350 Hz) show coherence with IMC angular control

The second bullet is indeed very strange since it seems that SRCL/PRCL contributes pretty much uniformly to the DARM background. It seems rather strange to me that sensing noie of SRCL/PRCL can couple up to those frequencies. One simple way to test it would be to add a band-stop filter at 1-2 kHz in PRCL and SRCL loops, and see if the coherence with DARM gets reduced. If not, it means that the same souce of noise contributes in a similar way to both RF signals (used for PRCL and SRCL) and DC signals at the AS port. I can imagine things like: high order modes and RF modulation amplitude noise...