I have an issue with some cheap HC-SR04 distance sensors, like the one described in this Arduino forum thread (http://forum.arduino.cc/index.php?topic=55119.0):
"...it doesn't appear to have an internal timeout for when it fails to detect an echo.
This sometimes results in the echo line staying high forever, even if you re-trigger a measurement.
The only way to get it to reset is by cycling the power."
One proposed solution is :"...When I detect the sensor is stuck, I simply switch echo pin to OUTPUT, put it into LOW state, and after a while re-set it to INPUT, then cycle again."
Do yo know if this solution is applicable to the EZB-4 and EZ-Builder? Or is there any other option you can think of ? (except buying new sensors, of course :D)