I can confirm that flashing the GPS xadow board following the process defined in this other forum post:
worked properly for me; my code changes I submitted above have addressed the longitude string parsing error.
The process is straightforward, assuming you have an 8266 board sitting around. Soldering 2 wires to the bottom pads of the GPS xadow part is required.
However, I have a new problem with the GPS code. It was true even before the flash of the fixed code. Every once in a while, the string returned for latitude or longitude is off by 2 orders of magnitude (e.g., 7200.ab rather than 72.yz). It’s not just a shift of the digits (as if the decimal place was in the wrong location).
More as I dig deeper