On my wash cycle I have the water level set at large it fills like it should. The rinse cycle it only fills about a 1/4 of what it should.
You will want to check to make sure that the screens on the water valve for the cold water are not clogged up. If the screen is clogged it will cause the unit to not fill properly. If this checks ok then you would want to check to make sure that the pressure hose is not clogged or kinked.