If the pump is new the most likely cause is a back EMF, are you using a RCD or MCB trip on the breaker?
If its tripping locally not on the MCB or RCD then yes this is likely to be a fault pump.
A small number of pumps will have defects when produced, which arises in the form of a failed bearing, washers or coil, which can cause these type of nuisance trips.
As such I would agree that this sounds like a faulty part and needs to be returned to the retailer.
Please let me know if I can be of any further assistance.