This is why you need to know how to navigate.
Have had about three GPSs quit on me. Then we toss them and get a new one. Then you have the joy of re-installing all of your way points. You do have the way points in your navigator's work book right!?
I for one practice and teach those "archaic" navigation skills. You will be surprised on handy those skills are in everyday operation of you boat, even if you are using a GPS.