Luckily all the GPS-based navigation systems as seen here are so robust!!!
Maybe, but perhaps a better description of modern airliner nav systems would be "computer based with inertial/GPS/Air data/radio input, blah blah..etc etc".
In this incident's case it looks to me as if the GPS side of the nav system was robust enough, but it's data was being disgarded because of system logic.
If the crew had been using a pure GPS nav system I somewhat doubt the incident would have happened.