Unable to connect using webdav (LibreOffice, Thunar/gvfs)

Hello.

I have just upgraded from ownCloud 8.2.5 to Nextcloud 9.0.51. The installation is on OVH shared hosting (pro2014).

I am unable to connect using webdav, either as LibreOffice remote file or from Debian Jessie xfce desktop using Thunar and gvfs backend. Both of these webdav connections worked without problems on my previous ownCloud installation.

There are no errors in the Nextcloud log (log level: everything), nor are there any entries in the webserver error logs.

The webserver access log shows 503 errors for gvfs and LibreOffice:
"OPTIONS /remote.php/webdav HTTP/1.1" 503 26 "-" "gvfs/1.22.2"
and
"PROPFIND /remote.php/webdav:443 HTTP/1.1" 503 - "-" "LibreOffice" "HEAD /remote.php/webdav:443 HTTP/1.1" 503 - "-" "LibreOffice"

Any ideas, please?

Thanks.

Raised as issue on GitHub: https://github.com/nextcloud/server/issues/223