After Upgrading to NC25 caldav does not work anymore

After upgrading to NC25, the caldav-synchronisation does not work anymore. If I try to copy the primary caldav-adress in calendar-settings, there is an error.
If I use DavX5, there is no calDAV-service recognized and an error will appear.
How do I use the calDAV function in NC25?

After deactivating all installed apps, Webdav started to work again. To copy the CalDav-Link does not work yet.