A brief follow-up on this since we discussed this at the meeting yesterday: the attached DV screenshot shows the full 2k data for a period of 2 seconds starting just before the watchdog tripped. It is clear that the timescale of the glitch in the UL channel is much faster (~50 ms) compared to the (presumably mechanical) timescale seen in the other channels of ~250 ms, with the step also being much smaller (a few counts as opposed to the few thousand counts seen in the UL channel, and I guess 1 OSEM count ~ 1 um). All this supports the hypothesis that the problem is electrical and not mechanical (i.e. I think we can rule out the Acromag sending a glitchy signal to the coil and kicking the optic). The watchdog itself gets tripped because the tripping condition is the RMS of the shadow sensor outputs, which presumably exceeds the set threshold when UL glitches by a few thousand counts.