Hi Bruce
The fault kind of makes sense with what you have described as it states its a Pump motor faulty transistor drive.
If its not a faulty IGBT then as its erratic it may be a loose wire or a bad connection to that part of the circuit. Best thing to do is strip it and see if the connections on the IGBT are loose and also check the pump circuit current sensor plug and wiring.
The info states either IGBT, or current sensor or the driver board.
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