The fluid level in the reservoir was looking very low and the level switch could not be lowered any further.  Re WP 3909, I ramped the pressure down slowly but the ISI still tripped.  Fluid was added to the reservoir and the level switch adjusted accordingly.  Ramped the motor speed back up, slowly, to ~80psi.  Pump driven at 15.2hz; the servo is in manual.  We have been unable to get this to drive the VFD; still working on this.