Hi Ross, possibly the drain hose is holed but with the filling on its own with dirty water, it sounds like it may be syphoning.Is the drain hose up in a loop or facing down.If down, lift it up and tie it up. this will stop it syphoning back.If the water goes to a stand pipe then possibly this is blocked.The machine will have to come out at some stage and properly inspected as the units will swell from the water. all the best.
FOXY
October 2008