Lower resonator trolley radial motor overcurrent was causing control system to drop out momentarily.  All controlled devices acted as expected and reverted to their fail-safe mode.  When system restarted 1-2 seconds later, all solenoids returned to their previous positions.

The cause was eventually traced to an unusual operation of the trolley.  In an attempt to limit trolley motion the drive switch on the control panel was repeatedly “tapped” in a rapid fashion.  This did not allow the motor to slow down enough to allow the starter winding to kick in which allowed large in-rush current.  The current was enough to load down the entire system including the power supply for the trolley controls, which caused the controls drop-out.

Later the same effect was observed to a lesser extent on the upper resonator trolley which used identical motors and controls.

Proposed solution is to either to limit large inrush current or preferably to replace the existing motor with a DC motor and controller.  A DC motor has the added benefit of now allowing true speed control.

No attempt is being made to modify the system until after the shutdown.  All trolley operators are being instructed to not use this method to attempt to control positioning of the trolley.  It is unlikely that it would help in positioning even if the system could handle the current overload.