Hey, @Fele thanks a lot for your report! - It looks like the client did not catch up fast enough with the server permissions after the upload. Usually, we query those every once in a while so the server does not get overloaded with requests. (e.g. the client will take a while to realize the admin disabled "sharing" for the whole server and adjust: https://github.com/owncloud/client/issues/4205).
It might make sense to adjust this time, after all, I'll try to measure the impact of the delay when uploading a file and report here back with my results.
In the near future; we want to move to a socket-based event triggering logic that will translate in clients catching up with the server in a more reactive way. You can follow up the progress in: