I habe a virtual machine with nextcloud 16 and a virtual machine with onlyoffice.
Also I have installes the OnlyOffice App and the documents are opend with onlyoffice.
But if I write content in the files and onlyoffice stores automatic, the content of the file do not store in the file in nextcloud.
Do you have same conditions as of https://github.com/ONLYOFFICE/onlyoffice-nextcloud/issues/118? if not, please provide a list of steps how to reproduce your issue and an relevant output of nextcloud.log (normally located inside of your data directory).
You may try to disable files_versions as workaround.
when you open a file via OnlyOffice app in Nextcloud the file is copied to the OO-server. In my setup the files in the folder /var/lib/onlyoffice/documentserver/App_Data/cache/. There is a Directory forgotten for all documents which were not saved back to Nextcloud.
If you know the Documents which were not saved back to Nextcloud you can simply open the documents again and use “File” -> “Download as…” in OnlyOffice.
If there are many documents in the forgotten folder you need to understand how the digit directory names are created. In former versions of onlyoffice app it was simply Nextcloud’s fileid. But this is dangerous since multiple Nextcloud instances can use same OnlyOffice server.
I hope these are enough informations to get your data back from your OnlyOffice instance.