With full lock, the H1:LSC-Y_TIDAL_REDTRIG_INMON has a value of 175000.  The H1:LSC-Y_TIDAL_REDTRIG_THRESH_OFF had a value of 10 and it takes almost 4 seconds to reach that threshold.  Meanwhile, the ISC was still driving HEPI and does so quickly causing the ISI T240s to be driven to trip.

In the attached 10 seconds trend, the lock loss is clear with the ASC TR SUM dropping along with the REDTRIG power.  The signal finally reaches 10 almost 4 seconds later seen on the TIDAL_CMD trace.  Meanwhile, ISC has rapidly driven HEPI >100um, quite quickly.  By then the T240s are too far gone (Red Trace #1) and will trip the WD.

Sheila & Daniel have increased the ON/OFF thresholds to 8000/5000.  This should work for 2 watt lock and reduce our delay to under two seconds--maybe enough.  But why is this suddenly a problem?  Or is it some series of unfortunate events that made it happen this time?  Scaling the thresholds with power is the better albeit complex solution.