I think there is a problem with the EventIterator.php. In rfc5545 it is described that a "RDATE" can occur inside a "RRULE". In such a case, the recurrence instances are defined by the union of occurrences defined by both the "RDATE" and "RRULE". In the current implementation, the "RRULE" is ignored completely when an additional "RDATE" is included in the "VEVENT". Therefore the EventIterator returns only the "RDATE" events and the original "RRULE" is lost.
Seems as somebody in 2016 already mentioned this: #347. I encountered such a vevent with RRULE and RDATE several times by now, so it seems to be used. Might be created by either thunderbird or DAVx^5.
I think there is a problem with the EventIterator.php. In rfc5545 it is described that a "RDATE" can occur inside a "RRULE". In such a case, the recurrence instances are defined by the union of occurrences defined by both the "RDATE" and "RRULE". In the current implementation, the "RRULE" is ignored completely when an additional "RDATE" is included in the "VEVENT". Therefore the EventIterator returns only the "RDATE" events and the original "RRULE" is lost.