With akonadi-server 18.04.01 (kontact 5.8.1) my calendar stopped synchronizing. The error I see on the console is: parse error from icalcomponent_new_from_string. string= "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<d:error xmlns:d=\"DAV:\" xmlns:s=\"http://sabredav.org/ns\">\n <s:exception>Sabre\\DAV\\Exception\\NotFound</s:exception>\n <s:message>Calendar object not found</s:message>\n</d:error>\n" org.kde.pim.davresource: DavGroupwareResource::onItemFetched: Failed to parse item data. Please let me know if I can provide more details or how to debug it further. I'm gladiac in #kde-devel @ freenode.
*** This bug has been marked as a duplicate of bug 397451 ***