Sorting of Photos

Hello,
I have a new NC installation, it is running on an odroid HC1 behind an Raspi2 reverse proxy. Everything works fine so far, NC is accessible via internet and I want to sync ma photos from iPhone as I did until to google Photos.
But the file sorting on NC is very strange, if I sort them by date ist ist different from the photos stored on the phone or on the google photos. I already deleted the files and re-synced with the option folders for years and months, but it didn’t work. some folders remain empty nevertheless if there are pictures existing which should be stored there. It seems that there is an issue in the iOS app reading the metadata from the pictures. Is this an know issue? Is there something that I can reconfigure to get this working?
Best regards
S