Writing to SMB shares via web


I have been playing with OwnCloud on CentOS and NextCloud as VM for a while now. In my environment I am using no local storage, but instead I access a SMB share which is hosted on a Windows Server 2012 R2. This host is also DC. Users authenticate via AD.

While I have no issues accessing my shares, I frequently run into trouble when I edit files via NextCloud Web.
Most of my files are plain TXT files. I can see and open them fine.
If I write anything to them, I get no more than maybe two chances to change things. But since the editor saves practically after each character, that’s quick.
If I copy the content from the file and close it, past the content to my editor, do my changes, copy them and paste them back into the document, I get away most of the time.
Editing right into the window of NextCloud always gives me an “error while saving” message.
Uploading works fine - most of the time.

This latest try with the VM downloaded from the official site is very orthodox with hardly any configuration done to the machine.
My previous OwnCloud-installation was a bit more customized, installed to CentOS and using modified SMBclient binaries and libraries to hunt down this issue. No progress.

Who has an idea?


Anything interesting/helpful in any logs (Nextcloud/Samba/Server 2012 event log)?