Ios, big memory use but no offline files active

I just got message from my iPhone that there is not much memory left. I checked iPhone storage and found Nextcloud app uses almost 50GB. After clearing the cache its little less, but still more then 30GB. I checked within the the app “manage offline files” but cannot see any. Also “favorites available offline” is not selected. I auto upload my iPhone photos and videos and the Photo folder is set to favorite. But I do not have them offline within the app. Only in iPhone photo app storage.
Please see screenshots. I use latest iOS app ( and server version 10 on an Freenas 9.
Autoupload works fine. On my daughter’s iPhone the app uses only few MB (and she does have much more photos).
Thanks for your help!

No idea? Or am I doing something wrong?

In your iOS app try Settings > Advanced > Clear Cache