not familiar with this particular make/unit but...
could be a blockage in an internal pipe from the bottom of the consender holder sump to the lift pump?
or maybe the lift pump is weak or intermitant/stopped. the lift pump pushes the water up from the bottom of the dryer (from the resoviour that fills from the water taken from the condensor unit) to the top water tray.
Mark Hunkin, January 2009