Aperture GPS Data not syncing to iOS

I just switched from iPhoto to Aperture and I really enjoy all the new fun! However, one thing is ruining it for me: My GPS data is not synced over to my iOS devices. I can't pinpoint what exactly goes wrong, I had all kinds of pictures: a) Camera w/ GPS b) Camera w/o GPS, data added with Aperture c) iPhone with GPS data etc.

Now before I clicked sync everything in Aperture had GPS data. After syncing, most of the GPS data is not available on the iPhone. However, it doesn't matter if the picture type is a, b or c! Sometimes they are with, sometimes they are without GPS.

I am using all the latest versions of Aperture, iTunes, iOS etc. I have synced a multitude of times. Deleted everything, synced again. No change.

It gets even stranger: although it is completely random which picture has GPS and which does not, this particular picture will NEVER have GPS even after a full resync.

Hope that is somehow understandable.