Since Firefox uses geoclue-2.0 for geolocation, maybe geoclue-2.0 is to be blamed:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1074427
- Bug#1090760: firefox: geolocation does not work, Mozilla Locat... Amr Ibrahim
- Bug#1090760: Maybe geoclue-2.0 is to be blamed Amr Ibrahim
