Some User can open PDF Files other cannot

I installed nextcloud 11 on my Server (Ubuntu 16.4). The Cloud is encryted. The Admin User copied all Data intothe Cloud an Creat Users and Groups and allowed all users of the group full access on the data.
Some of the users can work, the can open everything , especially those PDF-files, which other users cannot open.
They get following error message:
PDF.js Version 1.4.20 (build: b15f335)
Nachricht: Unexpected server response (0) while retrieving PDF "https://servername/remote.php/webdav

When they try to download, following message could be read in the Browser (Firefox 53):
Die Dateien unter https://Servername/remote.php/webdavpath and dataname.pdf?downloadStartSecret=code konnten nicht gefunden werden.

All installation and browser are german.

What can I do?

Thanks for your help

Baerin

I’m not sure about the latest development, but before sharing, all users had to login first to create keys for encryption. The typical error message was that you have to login first and then ask the owner to reshare the file with your again. Perhaps something new…?

Are you using external storage? It was designed to be secure on external storage, on local storage there is very little benefit and you potentially get a number of new problems you won’t have without :wink: