Still getting Stage1 actuator trips on the ISI stage1 followed 6 to 8 seconds later by a HEPI actuator trip.

The HEPI will stay closed loop for as long as I'm patient and I've had the ISI in full isolation for periods of time.  Sometimes the trips come shortly after the Stage1 of the ISI gets isolated and others it is when the stage2 is isolated.  But the trip is always the same--that is: Stage1 Actuator followed byt the HEPI Actuators.  These trips have an 8hz signal on them and the horizontal channels are overwhelmingly stronger than the verticals.   I've been following spectra and TFs between HEPI & the ISI but can't find the link, yet.  There is of course coherence between the HEPI Actuators and the ISI Stage1 sensors & actuators at the 8 hz peak.  The radomness may be the dependance on the wandering ground motion...  Still hunting

The Attached plot shows the problem peak in the position sensors which comes up with the HEP loops are closed; this seems independent of the ground noise but may be a problem when it wanders into the area.