Badplaas bruce

New out of box axpert 3kva (Easun) immediately reports error 5 (overheat or shorted output). It does this even with ac output wires not connected. There is no voltage on AC output terminals. Fans run full and continuous while PV connected and charging 48v battery bank (but fans turn off after 30sec. if PV wires removed). Also display continues to show the pv icon charging batteries even with PV input wires disconnected. PV input terminals show identical voltage as battery bank with PV wires removed both on display and with multimeter. triple checked all voltages, current, polarity correct and well within the units max limits. This is the 4th axpert I have installed so I am confident install is correct. I suppose it could be bad from the factory but that is not common. Trying to understand what component would cause these multiple issues. It is not helpful that a single error code (5) is used for both unit overheat and output short circuit.