Maria had a look at the coherence before and after the engament of the new 50 Hz FF (that occurred on March 13 at 14:30 UTC, as reported by Paolo). From the attached plots you see that the coherence with the UPS CEB channels reduced by about half in the wide region around 50Hz, also up to 54Hz (Figures 2 and 3) while the UPS spectral noise did not (Figure 1).

The daily BruCo plots confirm this: looking at the summary coherence projection, it is evident that the coherence in the 50Hz bump region reduced across March 13rd, and remained at this lower level since then: we attach here one Bruco summary plot just before, the one just after and the one of yesterday: Figures 4, 5 and 6

So we would conclude that also the reduction of noise in the wider region, well evident up to 54Hz, is related to the engagement of the improved FF (!)