How to filter a regular ticking out of a digital (on/off) signal?
Are you processing this data offline or in real time? If you're doing offline processing, or can live with a significant delay, then you could apply a simple filter as follows:


From each input sample, check to see if the sensor reported "on".
If it did, search for a "few" 16-minute periods in each direction and see whether the sensor reported "on" there as well. This is a noncausal operation; if you're processing data in real time, you can search in both directions by first applying a large enough delay to the signal.
If there are "enough" consecutive "on" samples at the spurious period in either direction, suppress the "on" indication from the sensor.


This should suppress the unwanted square wave of "on" indications, but as indicated in the comments, it also could possibly suppress valid "on" reports. The "few" and "enough" parameters you'll have to select yourself based upon what is reasonable given the overall behavior of your system. Basically, you want to set "few" so that you're looking at enough spurious periods to make a good decision. You'll want to set "enough" small enough to suppress short bursts of the spurious period, but large enough to avoid suppressing too many valid "on" indications that happen to be separated by 16 minutes.