It seems that the "google.loader.ClientLocation" isn't always filled with an value, for more information see:
http://stackoverflow.com/a/14243526
You can find moren information about how this works in the Pronamic Google Maps plugin in the code:
https://github.com/pronamic/wp-pronamic-google-maps/blob/2.2.3/js/site.js#L81
It the "google.loader.ClientLocation" varailable is NULL, we won't be able to center the mashup to your location.