I followed tips on hardware check and confirmed that my GPS radio, antenna and the connector in between are all intact; I also apps like "GPS Test", "GPS Status" and "Radar"; all showed 2 or more satellites appearing and then disappearing intermittently. I did manage to get a brief lock and confirmed so when Google Maps pinpointed my position.
I stand to be corrected when I say that "I'm now convinced that it is the combination of several GPS-using apps in my phone that are causing the problem (not locking-on) as they compete to use that single resource (the GPS) in their own ways, at the same time. This problem seems unique to the phone when running Android-5.0 as I never heard of it happening on its original Android-4.3 and 4.4 or even in my previous phone (Samsung GT-I8262) which ran 4.1.2
Does anyone know the USSD for calling up the hidden Samsung service menu for sensors test? I do know that *#9900# calls up the memory-dump menu.
Read more: GPS not locking on to signals in my Samsung Galaxy Note 3 (Android-5)