Community document server fails to store changes into Nexcloud

We recognised similar Problem: Creating Office Document, edit, close it.
The synced document is empty when it’s opened in Word.

I did then take a closer look with ftp: the content of OnlyOffice documents is stored in different folder than the origin doc folder at file system.

This looks like the doc content is separated from the base file.

How to handle syncronisation of OnlyOffice documents ?

Rolf