One of the things that was introduced recently into the HTC One M8 echosphere was the ability to use a WiFi connection to make and receive phone calls. To do this, you have to give the address that that WiFi connection corresponds to and your GPS agrees is right, in case there’s an emergency and emergency services needs to know where you’re at.
Unfortunately, this seems to be causing the GPS to go out at random times on several ROMs (I’m reading it’s across the board and even on stock, but I won’t claim to know that for sure).
The issue it seems is when WiFi calling is enabled, it will stick your location to that predetermined address and you may be stuck there until such time as you reboot your phone. Turning location services on and off doesn’t do anything, and disabling WiFi calling doesn’t do much.
If you’re lucky enough to get GPS to work after exiting the WiFi calling area, it’s prone to lose signal and never pick up again until a reboot.
If you’re experiencing the issue, it seems there are two solutions that work or don’t work for people. These are to activate the hardware GPS in some fashion before you enable WiFi calling, or to simply not use WiFi calling at all.
Unfortunately, only the “not using WiFi calling” option works for me, so your experience may vary.
If you’re interested in seeing if you have the GPS issue, download GPS Status and Toolbox and see if you get a satellite fix when you’re on WiFi calling or after you disable it.
On a happy GPS, you’ll see a bunch of satellites and get multiple locks. If you’ve got the bug going on, you’ll see nothing and it will search for GPS forever.
Hopefully this will not mirror the 11 months of GPS hell the EVO 4G LTE went through before Sprint finally pushed a fix.
On the PRL front, you can’t check for a PRL update if you’re connected to WiFi calling. This is a pretty easy fix, though: disable WiFi calling, check for PRL update, reenable WiFi calling.