I suspect it was the random part that Peltonlevel found scary as I think you'll find he has a fairly good idea of how these things work.
There will always be an N, the important thing is you know what the value of N is and you know exactly what the system will do when it reaches that point. If it drops tracks you really need to know the rules by which it will do that, just randomly dropping tracks would not be acceptable to most safety engineers or the Safety Regulator.
What we don't know from the brief details on this thread is whether the MUAC tracker actually failed or was dropping so many tracks that it was unusable.