If you're brave you can take a walk to the sensor and kick it a few times so it starts working again.
Jokes aside, the way i see it is the things OP is warning us about are not always happening at the present moment, but are 'reverberating through time' so to say. I remember a certain radiation monitoring sensor going berserk a few months before the actual event that triggered it happened. My guess is a nuke with a 100km radius of radioactive fallout could be dropped there in the near future. Or something else that can cause radiation in aforementioned area will happen, what exactly i have no idea.
But i'm just a schizo, so don't take what i say too seriously.