Nextcloud calendar One Calendar sync issue

ℹ️ Support
1

When syncing Nextcloud calendar with One Calendar by Code Spark only two of three calendars are syncing. One Calendar is reporting a CalDav error.

I have three calendars in Nextcloud

  1. personal calendar (owned by me and shared with other users)
  2. family calendar (owned by me and shared with other users)
  3. wife’s calendar (owned by my wife and shared with me)

Family calendar and wife’s calendar sync correctly. My personal calendar does not sync at all and reports an error.

Syncing in One Calendar using CalDav and the iOS CalDav link.

Error log from One Calendar:

Dav.Client.DavException: Caldav error in decoding data ---> System.Exception: Unterminated escape sequence
   at CardDav.vCard.Common.Decode(String) + 0xec
   at CalDav.iCalendar.Common.Property(TextReader) + 0x199
   at CalDav.iCalendar.Event.Deserialize(TextReader, Serializer) + 0x76e
   at CalDav.iCalendar.Calendar.Deserialize(TextReader, Serializer) + 0x26e
   at CalDav.iCalendar.CalendarCollection.Deserialize(TextReader, Serializer) + 0x7b
   at CalDav.iCalendar.Serializer.Deserialize[T](TextReader) + 0x4c
   at Dav.Client.CalDav.CalDavServerCalendar.<GetAllEventContent>d__29.MoveNext() + 0x570

   --- End of inner exception stack trace ---
   at Dav.Client.CalDav.CalDavServerCalendar.<GetAllEventContent>d__29.MoveNext() + 0x907
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x21
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0x70
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task) + 0x38
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task) + 0x17
   at CalendarApp.CalDavBaseProvider.CalDavBaseAccount`1.<GetAllEventsData>d__14.MoveNext() + 0x10a
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x21
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0x70
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task) + 0x38
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task) + 0x17
   at CalendarApp.CalDavBaseProvider.CalDavBaseAccount`1.<SyncReceiveCalendarFromProvider>d__13.MoveNext() + 0x492
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x21
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0x70
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task) + 0x38
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task) + 0x17
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult() + 0xb
   at CalendarApp.ProviderBase.AccountProviderBase`9.<SyncReceiveCalendar>d__99.MoveNext() + 0x21b

ObjectData: <d:response xmlns:d="DAV:">
  <d:href>/remote.php/dav/calendars/Glen%20Wesley/Glen%27s%20Diary%20(Google%20Calendar%20import)/_8gq42e1h6kq3ib9g8h348b9k60sjeba28cq48ba48l2jad1o8gq3ihi270-%223059256802554000%22</d:href>
  <d:propstat>
    <d:prop>
      <d:getetag>"dd0f9880a1c553b1e96f589aa5f1fb1e"</d:getetag>
      <cal:calendar-data xmlns:cal="urn:ietf:params:xml:ns:caldav">BEGIN:VCALENDAR
VERSION:2.0
PRODID:NextCloud Calendar
BEGIN:VEVENT
UID:6-_8gq42e1h6kq3ib9g8h348b9k60sjeba28cq48ba48l2jad1o8gq3ihi270-"3059256802554000"
SUMMARY:Haircut
SEQUENCE:2
LOCATION:Musket &amp; Bayonet
DESCRIPTION:Your appointment booking has been confirmed at Musket and Bayonet Pty Ltd\n\n\n\n\n\n\nAppointment confirmed\n\nHi Glen,\n\n\nThe following appointment has been booked:\n\n\nMusket and Bayonet Pty Ltd\nFri, 12 May 2017\nHaircut with Jimmy at 10:30AM\
STATUS:CONFIRMED
CREATED:20170514T235648Z
LAST-MODIFIED:20180622T004641Z
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER;RELATED=START:-PT15M
END:VALARM
DTSTART;VALUE=DATE-TIME:20170516T003000Z
DTEND;VALUE=DATE-TIME:20170516T010000Z
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR</cal:calendar-data>
    </d:prop>
    <d:status>HTTP/1.1 200 OK</d:status>
  </d:propstat>
</d:response>

Inner exception: System.Exception: Unterminated escape sequence
   at CardDav.vCard.Common.Decode(String) + 0xec
   at CalDav.iCalendar.Common.Property(TextReader) + 0x199
   at CalDav.iCalendar.Event.Deserialize(TextReader, Serializer) + 0x76e
   at CalDav.iCalendar.Calendar.Deserialize(TextReader, Serializer) + 0x26e
   at CalDav.iCalendar.CalendarCollection.Deserialize(TextReader, Serializer) + 0x7b
   at CalDav.iCalendar.Serializer.Deserialize[T](TextReader) + 0x4c
   at Dav.Client.CalDav.CalDavServerCalendar.<GetAllEventContent>d__29.MoveNext() + 0x570