Ocasionally (but getting more regular in last couple of days), the image location is not storing properly - it's usually gallery_googlemaps_lat. As you can see from attachment, in the datastore browser, the value is absent, but if you choose the modify button, there is a an accurate value for gallery_googlemaps_lat.
What is odd is that it almost seems to be some characteristic of the image. If the value doesn't 'take', you can't edit it manually - that images map will always be broken. So you delete the image and try again - same result. Took two hours yesterday to get one image in, and even then I had to upload a different picture to create the gallery, and then go back and change it to the one I wanted.
Doesn't seem to be characteristic of the chosen location - it will happen whether you choose a specific address like '21 Alum Rock Road', or a generic one like 'Birmingham'. This is one such image - http://ourtownstory.co.uk/iamtimbo/gallery/278/aston-local-board-offices-c-1897 . The data is there somewhere though - the box that says 'Nearest places to this image' gets its data from the gallery_googlemaps fields.
Baffled.
updated by @iamtimbo: 04/25/15 09:24:02AM