2449.25 Hz line (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=14855) is visible in BS oplev PIT, but not in BS oplev YAW nor ITMX, ITMX, PR3, SR3, even when no LSC feedback goes to BS.

That line in OL signal becomes bigger when the IFO is in-lock even with the butterfly band stop, but the OL damp also seems to excite the motion at an amplitude that is comparable to the LSC signal through the band stop (attached right bottom).

Based on these observations, I moved the butterfly notch (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=14898) from M3 ISCINF to M2 coils so that everything is stopped (see the filter settings in the attached).