After the repair of the faulty LEMO cable, I left MC1 with it's watchdog off overnight. Unfortunately, it looks like the problem still persists. The first attachment shows a second trend plot for the past 15 hours. Towards the left end of the plot, you can see where I re-connected the LEMO cable for the LR/UR channels.
A couple of months ago, I added a BLRMS block for the IMC optics that calculates BLRMS for the shadow sensor output as well as the coil output. Looking at this trend overnight, I noticed that the glitches appear in the coil outputs as well, as shown in the plot below, which is for a 1 hour stretch last night (I used the full data from a 16Hz coil output channel and not the BLRMS, I am not sure if there is a DQ'ed version of the coil outputs?).
Zooming in further to one of these glitches, we can see that the glitches in the coil and shadow sensor signals are in fact coincident.
But given that the watchdog was turned off all this time, the only voltage going to the coils should be the DC bias voltages.
So does this not support the hypothesis that the problem lies in the part of the signal chain that supplies the bias voltage to the coils?
Never mind, the "coil output" channel isn't a true readback of the voltage to the coil, but is the calculated damping output (which is not sent to the coils when the watchdog is shutdown...