iOS 11 - no upload from iPhone to Computer

Since the upgrade of my iPhone 7+ to iOS 11 I got the following problem.
I open a file stored in SeafilePro i.e. with Excel, Word, Pages … I work with the file and at the end I save it to seafilepro. Going back to seafilepro, I have to make it actually by hand; then I see a changed information about size and point of time of changing.
I go to my computer, open Seafile in a browser and see the changing, too. I go to my local directory and there is no change. If I download the file via browser from server, it got the size of 0 byte.
What I describe is only a problem of existing files.
I know two workarounds, both very uncomfortable: On IPhone export the file from Seafile to pages i.e., then delete the file in iPhone-SeafilePro, work with the file and then save to Seafile. Better: Export a file via eMail and then on a computer overwrite the file.