J. Kissel, H. Radkins, J. Warner, [M. Ross remotely] FRS Ticket 13417 As we continue to investigate the problems with BRSX glitching, we've removed it's tilt subtraction from the sensor correction path at EX (see above cited FRS Ticket and LHO aLOG 51309). Once we did, we were able to successfully get through the entire lock-acquisition sequence as normal -- hence the reported observation stretch in LHO aLOG 51324 and 51325. As recommended by Michael we took a look at the *raw* raw BRS signal -- the fringe patterns as measured by the CCD. To do this requires killing the BRS c-code and logging in to Beckhoff ***, so we've done so and captured the video -- posted under G1901492. A frame-by-frame instantaneous plot of the fringes are on the left, and the corresponding long-term time-series of the calculated rotation signal from it is on the right. For the left plot, the lefter of the collection of fringes is the reference light reflection, and the righter is the reflection from the rotation sensor's suspended beam. One can see at the start of the video, that 2 glitches have happened already in the past 500 seconds, one at ~150 seconds and another, smaller at ~250 seconds. Then, right at the start of the video (within 2 seconds of it), a new glitch starts, and one can see *all* the fringes -- the reference fringes a little more clearly than the that beam fringes drop in amplitude by (0.9 - 0.85)/0.9 = ~5%. The fringe heights restore (and the glitch stops) at around 5-7 seconds. Best to download the movie and open in a player where you have the ability to control frame, since it's a subtle affect, best seen on repeat or flipping back and forth between YES glitch and NO glitch frames. Where Michael's previous experience seeing this behavior was an actual insect "bug" walking across the CCD, this appears to be a more systemic problem, of either - sensitivity drops in the CCD, or - light level drops from the LED light source. The investigation continues... *** Reminder that we wouldn't *have* to kill the BRS c-code to look at diagnostic signals, if the recent attempt at a code upgrade hadn't failed for unknown reasons LHO aLOG 50178. Another reminder -- this is the oldest BRS, installed in Aug 2014 -- see, e.g. LHO aLOG 13296.