I don't think you read my question e.g. "No component appears to be leaking at all" and "insulation gets very wet under the detergent dispenser but dry elsewhere" because these point to where the leak is situated. However your comment that too-high water pressure wouldn't do this is helpful. I think all the water into the drum is fed via a little nest of pipe junctions into a sluice under the detergent slot and through a narrow slot (pointing upwards) at the outer end of the detergent slot, so it then picks up the detergent on it's way down the slot to the drum. The leak appears to be somewhere there. We've had this washer 7 years. My wife tends to be very generous with the powder but then she always was, and it didn't leak then. Our water pressure is higher than it used to be: would throttling it with the mains shut-off (screw-down) tap be effective and OK for the machine?
Thanks! Chris (also called Laughing Jacket).