It _is_ unusually low, but there are things that can cause it besides AI destabilization.
Overpopulation rarely will cause something like that, but abnormally high planet classes with out racial morale improvements can get to the point where something like that can happen purely from overpopulation. The population growth, planet quality, and morale interactions were tweaked to make it very difficult to run into, though, as to get to those sort of planet classes you usually need the Planet Quality techs, all of which are after _4D Phasing in the tech tree (and thus you should have at least a racial +50% morale bonus).
The Precursor terraforming event, Earthworms terraforming event, and the Planet Quality racial bonus from the setup screen could possibly get you into that area when you colonize class 26s, but even then, you shouldn't have a problem.
~SDC~