I see. Well I think the lesson learned is to always inspect your device fully during the 14 day evaluation period despite if you have other ways that can do the job. The way I look at it is that unless I have phone insurance this will be my device for the next 2 years so I would sacrifice using any other devices I was relying on temporarily and be damn sure this device is not faulty. I sure as heck am not waiting a month later to test out whether my GPS, Bluetooth, Wifi, 3G/4G data, NFC, phone calling, voice/data reception, etc are working or not. Like the GPS issue, I understand you car has a built navigation system but you could have verified it by maybe launching the Google Maps/Navigation app and letting it route you to work or whereever you were going in the background just to test out the GPS functionality.
I can't comment on the RF issues you were having but I feel the GPS issue could have been easily discovered and should have been resolved during your 14 day period.