[NC 14] Cannot sync calendars since updating to RC3

The Issue:
Since NC 14rc3 I no longer can sync calendar events to Davdroid or any other caldav client (tried with Thunderbird/Lightning on desktop as well). I updated today to 14rc4 but it didn’t resolve the issue.

Expected behavior:
I should be able to sync calendars with mobile and desktop calendars.

==========================
Specs:
Nextcloud 14rc4 (upgrade from 13 through updater)

Ubuntu 16.04

Apache
Server version: Apache/2.4.18 (Ubuntu)
Server built: 2018-06-07T19:43:03

===============
PHP
PHP 7.0.30-0ubuntu0.16.04.1 (cli) ( NTS )
Copyright © 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright © 1998-2017 Zend Technologies
with Zend OPcache v7.0.30-0ubuntu0.16.04.1, Copyright © 1999-2017, by Zend Technologies

=====
Database
mysql Ver 15.1 Distrib 10.0.34-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

In my logs I see this whenever I try to connect:

LogicException: This is not supposed to happen

/var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php - line 345:

OCA\DAV\CalDAV\Plugin->getCalendarHomeForPrincipal("principals/groups/admin")

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/PropFind.php - line 98:

Sabre\CalDAV\Plugin->Sabre\CalDAV\{closure}("*** sensiti ... *")

/var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php - line 349:

Sabre\DAV\PropFind->handle("{urn:ietf:p ... t", Closure {})

Sabre\CalDAV\Plugin->propFind(Sabre\DAV\PropFind {}, OCA\DAV\CalD ... {})

/var/www/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105:

call_user_func_array([ OCA\DAV\Ca ... "], [ Sabre\DAV\ ... }])

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 1059:

Sabre\Event\EventEmitter->emit("propFind", [ Sabre\DAV\ ... }])

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 981:

Sabre\DAV\Server->getPropertiesByNode(Sabre\DAV\PropFind {}, OCA\DAV\CalD ... {})

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 1666:

Sabre\DAV\Server->getPropertiesIteratorForPath("principals/groups/admin", [ "{urn:ietf ... "], 0)

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 359:

Sabre\DAV\Server->generateMultiStatus(Generator {}, false)

Sabre\DAV\CorePlugin->httpPropFind(Sabre\HTTP\R ... "}, Sabre\HTTP\Response {})

/var/www/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105:

call_user_func_array([ Sabre\DAV\ ... "], [ Sabre\HTTP ... }])

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479:

Sabre\Event\EventEmitter->emit("method:PROPFIND", [ Sabre\HTTP ... }])

/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254:

Sabre\DAV\Server->invokeMethod(Sabre\HTTP\R ... "}, Sabre\HTTP\Response {})

/var/www/nextcloud/apps/dav/lib/Server.php - line 293:

Sabre\DAV\Server->exec()

/var/www/nextcloud/apps/dav/appinfo/v2/remote.php - line 35:

OCA\DAV\Server->exec()

/var/www/nextcloud/remote.php - line 163:

require_once("/var/www/ne ... p")

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Does anyone have any idea how to fix this? I was stupid enough to accidentally switch to the beta channel in the updater which is why I upgraded. The server is my production environment :confused:

I’ve created a github ticket for this. Located at: https://github.com/nextcloud/server/issues/10727