As previously mentioned, the specification assures 600V isolation between output circuit and chassis ground.
The essential new information is that you repaired the power supply. In this case incorrect repair or an previously existing isolation fault, e.g. defective Y-capacitor might have happened.
My suggestion would be to perform always an isolation test after repair.
I think there's no other option for the customer than returning the device. Or, if you suspect a customer handling fault, make clear that continuity test verified the isolation fault inside the power supply.