THIS FIXED IT: So @djtroyan pointed me in the right direction. Unbelievably, for me it was hardware. I was split between the two, software vs. hardware, but I was leaning toward software. If you've seen my posts to this thread, I was also a launch day iPhone 6 buyer. My phone had been dropped a few times and I've also needed the screen replaced twice. Either way, my phone's body was badly damaged and it was actually bent a little (I've been more careful recently). I am not 100% sure what did the trick for me, but here's my fix and links to the parts that worked in my case.
- WiFi antenna signal flex cable
- WiFi antenna signal cover bracket
- Rear cover panel and mid frame assembly (I was skeptical about the quality of this, but it's about 99% identical to the original and 100% better looking than my original phone body)
- Vibrator (this isn't part of the GPS fix, but I can confirm it's a good part if yours is broken)
I used "GPS Status" from the app store to monitor what was going on with my phone. Before the repair it showed "Poor Fix" and "No Fix" constantly. I followed the iFixit guide for all the repairs and they're awesome. The flex cable was the last to arrive, so I started with the body the other day hoping it would do something. I noticed that my phone had finger prints throughout (probably from the screen replacements from the Apple store, don't they use gloves?). Using qtips and Windex (I thought that was a strange suggestion, but iFixit recommended it along with isopropyl alcohol, which I didn't have), I did a thorough cleaning of all the contact points on and off the logic board and brackets. It's important for these to be clean for the phone to work properly, if you don't have latex gloves or finger cots, order some from amazon when you order your parts. After the cable came in, I opened the phone back up and removed the logic board and flex cable and took a look at the flex cable with a magnifying hood (I bought this for another project and it's amazing when working on phones, watches or anything small) and noticed the center connection port on one of the 4 connection ports was broken off! I'm not sure if this was me, or if the original cable was a defect and was weak to begin with, but I took my time and didn't rush any of this and was very careful with every step, who knows. These connections are extremely tiny, anyways...
Conclusion:
I am so done with this issue and repair, this has been something that has been plaguing me for months now and was really making me angry, plus the lack of support at Apple wasn't helping. I really hope this is a step in the right direction for all of you and fixes your phones as well (for the brave that are willing to take this sucker apart). Remember, this was what fixed the problem for me and the issues some of you are experiencing could very well be something different.
At the end of the day, I have the look/feel and functionality of a brand new iPhone 6
*disclaimer, take this repair on at your own risk, or use this example as a reinforcing argument at the Apple genius bar