As shown in Fig.1, ISS guardian went to DOWN at first (top panel).
I haven't checked that what ISS guardian do in DOWN state but SYS_SDF guardian (2nd top panel)
detected the change in EPICS records with 4 samples delay in 16Hz (250ms) from ISS DOWN.
After then, IFO, LSC_LOCK, and IMC guardians (3rd-5th top panels) detected the lockloss with 6samples delay in 16Hz (375ms).
When IFO guardian detected changes in EPICS records related to the ISS DOWN,
LSC_LOCK guardian were still in OBSERVATION state and IFO guardian spoke at the same timing as
LSC_LOCK guardian moved from OBSERVATION to LOCKLOSS.
I'm not sure why LSC_LOCK guardian has such delays to detect the lockloss of ISS.
But this delay is the cause that IFO guardian spoke.
By the way, before ISS was lockloss, amplitude of CARM feedback and IMMT1 trans QPD signals became large as shown in Fig.2
On the other hand, MCE trans didn't detect such behavior until just before lockloss.
If ISS lockloss was caused by same EQ, we need to why the delay was occurred between ISS and LSC_LOCK guardian.
If it is not related to EQ, this is just an accidental coincidence.
Even error and feedback signals of ISS are not DQ-ed. So there may be no enough channel to investigate it...
