When tub temp. drops to 80-85f flow sensor points will close allowing tub to heat to 90-93f then sensor points open the 'flo' sign flashes and the tub is prevented from heating to 105f. Is the sensor bad or is it getting bad info from the circuit board? Mode is 'standard', not economy, have turned tub off for 30+ minutes then turned back on hoping things will reset....no luck.