Year view not showing location summary
I have a problem with the new photos app on iPhone6 and Yosemite 10.10.3.
In the "year view" places where the photos were taken can usually be accessed in a map (e.g. "United States, Germany and 3 more >").
I have several years of photos and this does work for most of them, but for 2 years (2013 and 2014) there is no location or countries displayed I could tap on to open the map view so I can see what places I visited in those years.
When I zoom in to collections or moments however, every single photo does have location data.
The photos app seems to fail summarizing my places. The problem is the exact same on iPhone and on the new photos app in Yosemite (turning on or off iCloud photo library doesn't make a difference here).
Also tried the following: I deleted all photos from my iPhone and sync them again via iTunes. When I did this while having the photos app open in the year view, I could see that the years 2013 and 2014 at first have this link to the map but as more photos are synced both disappear.
Any ideas on this? Please help
iPhone 6, iOS 8.1.3, Photos App on Mac and iPhone