Calendar notifications cannot be closed anymore

Dear all,

I have a current nextcloud 11 running with combination of nginx. As client thunderbird on windows is used.
I got a notification for a calendar entry which I cannot close anymore (it worked in the past, maybe it got broken by the upgrade to nextcloud 11, but I’m not sure).

I checked the logfiles and a 404 is returned.
The URI that is called is:
2017/01/06 10:13:52 [debug] 81650#101056: *20 http2 http request line: "PUT /remote.php/dav/calendars/idefix/contact_birthdays/ HTTP/2.0"

2017/01/06 10:13:52 [debug] 81650#101056: *20 http fastcgi header: "Status: 404 Not Found"

If I check the log from nextcloud I see:
Sabre\DAV\Exception\NotFound: HTTP/1.1 404 Node with name ‘’ could not be found

/usr/local/www/nextcloud/3rdparty/sabre/dav/lib/DAVACL/Plugin.php - line 898: OCA\DAV\Connector\Sabre\DavAclPlugin->checkPrivileges('calendars/idefi...', '{DAV }write-con...')
[internal function] Sabre\DAVACL\Plugin->beforeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/usr/local/www/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105: call_user_func_array(Array, Array)
/usr/local/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 466: Sabre\Event\EventEmitter->emit('beforeMethod', Array)
/usr/local/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254: Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/usr/local/www/nextcloud/apps/dav/lib/Server.php - line 227: Sabre\DAV\Server->exec()
/usr/local/www/nextcloud/apps/dav/appinfo/v2/remote.php - line 30: OCA\DAV\Server->exec()
/usr/local/www/nextcloud/remote.php - line 165: require_once('/usr/local/www/...')

Has there something changed with the new version that can cause this problem or is the problem located in a necessary change in the nginx configuration?

Thanks a lot for tips.

I don’t remember major changes for the nginx configuration between NC 10 and 11. If it just broke after this upgrade, it’s the best to report it directly to the bugtracker.