Just as a hint, don't know if it has to do with your problem. Using the builtin calendar I had some strange errors regarding birthdays. Sometimes they were starting on correct day and somewhen moved one day ahead. In details they still showed correct starting date. Probably this got fixed by last FW update, I didn't look into it for a long time.
Nevertheless, currently all my events are showing up correctly. But I don't have recurrent non-daily events currently. ... but I could test ....