The restarter checks for multiple things, including memory usage.
I've ran my test core for about an hour or so and I noticed that the core allocates and free's memory on a regular basis so the restarter doesn't give false positives.
It seems like your core doesn't do very much while idle though, not even allocating a few bytes of memory.
I recommend that you only run it while the core is actually busy and there are people connected to it ( doesn't have to be many players, even just 1 is sufficient ).
Also setting the threshold higher will reduce the chance of a false positive core freeze.