The water level sensor is not adjustable by the home handyman. The pressure tube from the bowl up to the sensor may be blocked but that would normally result in overflow most if not all the time. More likely to be a faulty inlet valve not shutting off. Check by lifting the lid during fill several times. Water should shut off immediately lid is lifted or start/pause is pressed. If it hesitates for a few seconds or does not stop then change the inlet valve.
Lincoln Appliance NZ, October 2009