ONLYOFFICE on external server ... IMPOSSIBLE to configure

I am running into a wall.
Cannot set correct settings for onlyoffice.

Removed the onlyoffice app from the installation (in apps)
Have removed all settings and configuration for onlyoffice (in config and in occ)
When I install the ONLYOffice app it will set its config to the ‘internal’ onlyoffice app.

When I set the DocumentServerUrl to the correct setting, (either in the config screen or with occ), it disregards the setting and keeps sending users to the internal /app/onlyoffice app.

Setting done with:
occ config:app:set onlyoffice DocumentServerUrl --value="<my server address>/documentserver/" --update-only

I don’t seem to be able to get the correct settings in nextcloud!

The whole thing works in docker, I have a separate container for onlyoffice and a proxy. The proxy works fine! When I connect to my own url /documentserver/ I get the welcome-screen for this container (the onlyoffice container)

Internally the container has a working connection, however, the setting for internal connections seems lost or missing.

Any advice is welcome!