The global positioning system (GPS) is a space-based radio-positioning and time-transfer system. GPS satellites transmit signals to proper equipment on the ground. These signals provide accurate position, velocity, and time (PVT) information to an unlimited number of users on ground, sea, air, and space.
I'm not too experienced with code including external memory, but i believe there was an error with the code mixing that either mixed lines of code up or got rid of code to save files onto your device. Try looking up code for the device, see if that helps at all.