First I have upgraded all Androids to client 3.5.1.
On a Linux client, I have a file README.txt that automatically gets modified once per hour. It gets synchronized to the nextcloud server immedeately.
On all clients, the file README.txt has been downloaded manually.
After a number of hours it turns out that all clients except one automatically update the local copy of the file.
On the misbehaving client the following happens.
The initial (manual) download of the file README.txt goes well. After a while, when the file has been modified on the server and the client detects this, the file gets a red cross and there’s a notification “Download failed - Could not download README.txt”. When I use the nc client file browser and click on the file I get the same error. The only remedy is to remove the file locally and download it again, manually. But the next time the file is changed on the server the same download error occurs again on the client.
It looks as if the client has access rights to create files, remove files, read files, but is not allowed to overwrite existing files…
FWIW, this client is running on Asus Z300M with Android 7.0.