I made some headway on the GPS problem today. I spent a long time on chat and then the phone with Samsung support. First we did a soft reset, which didn't help. Then we did a hard reset which restores the phone to the factory preset. That worked! After the reset, my phone connected quickly and easily to the GPS. On a trip around town, I did lose the signal for a bit, but the rest of the time, the navigation performed really well. I'm now in the process of reinstalling my apps, a few at a time, and then retesting. I think I'll try not to install anything I really don't need. I'm not sure if it was an errant app that caused my problems, but I'm going to be more careful, just in case.