I can reproduce the problem. The (a) problematic event isBEGIN:VEVENT DTSTART;VALUE=DATE:20170820 DTEND;VALUE=DATE:20170821 EXDATE;VALUE=DATE:20180415 EXDATE;VALUE=DATE:20181216 EXDATE;VALUE=DATE:20190120 EXDATE;VALUE=DATE:20190818 RDATE;VALUE=DATE:20170916,20171014,20171118,20171216,20180120,20180217,2018 0317,20180519,20180616,20180714,20180818,20180915,20181020,20181117,2019021 6 RRULE:FREQ=MONTHLY;BYDAY=3SU UID:firstname.lastname@example.org …
This is an event without end (no COUNT or UNTIL in RRULE), and it seems that the existence of RDATE/EXDATE in such events can’t be processed by the Android calendar provider, which sends:icsx5 : Found VEVENT: email@example.com icsx5 : firstname.lastname@example.org not in local calendar, adding RecurrenceProcessor: DateException with r=FREQ=MONTHLY;WKST=MO;BYDAY=3SU rangeStart=135390560256 rangeEnd=9223372036854775807 CalendarProvider2: Could not calculate last date. CalendarProvider2: com.android.calendarcommon2.DateException: No range end provided for a recurrence that has no UNTIL or COUNT. CalendarProvider2: at com.android.calendarcommon2.RecurrenceProcessor.expand(RecurrenceProcessor.java:768) CalendarProvider2: at com.android.calendarcommon2.RecurrenceProcessor.expand(RecurrenceProcessor.java:663)
So, it seems that such events are not supported by Android.