Error 1550 hen syncing Calendar

[pope-]

Hello MacRumors,

When I open the Calendar app it does not sync with iCloud. It shows a ! next to the iCloud title (see attachment). When I click on this a popup appears that reads:

The server responded with an error.

There was an unexpected error with the request (domain NSCocoaErrorDomain / error 1550).

The weird part is that when I add events to my calendar through my iPhone it syncs with icloud.com.

Here is the output from system.log:

Aug 19 17:42:10 macbook CalendarAgent[193]: [com.apple.calendar.store.log.caldav.queue] [Account refresh failed with error: Error Domain=NSCocoaErrorDomain Code=1550 "items is not valid." UserInfo=0x7fdac644da20 {CalDAVErrFromRefresh=YES, CalManagedObjectType=CalManagedCalDAVCalendar, CalGroupUID=56023E11-3F6F-40E8-B753-1624C2B35D7D, CalCalendarUID=E757C4B9-9474-4C19-A755-81B0D15CD914, NSValidationErrorValue=Relationship 'items' on managed object (0x7fdac62dd9f0) <CalManagedCalDAVCalendar: 0x7fdac62dd9f0> (entity: CalDAVCalendar; id: 0x7fdac62398d0 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/CalDAVCalendar/p6> ; data: {
alarmsDisabled = 0;
cTag = nil;
calendarPath = "/195385818/calendars/home/";
canBePublished = 1;
checked = 1;
color = "(...not nil..)";
colorString = "#0E61B9FF";
defaultAlarmSet = nil;
group = "0x7fdac453d210 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/CalDAVPrincipal/p4>";
isAffectingAvailability = 1;
isDelegate = 0;
isEnabled = 1;
isEventContainer = 1;
isRenameable = 1;
isTaskContainer = 0;
items = (
"0x7fdac62e08d0 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p79>",
"0x7fdac62b6280 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p133>",
"0x7fdac6284770 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p61>",
"0x7fdac625c8f0 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p120>",
"0x7fdac626abd0 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p164>",
"0x7fdac6213610 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p72>",
"0x7fdac62a8ec0 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p57>",
"0x7fdac62ce480 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p173>",
"0x7fdac6276210 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p176>",
"0x7fdac6235a80 <x-coredata://56DFFFC7-B8F6-4195-A1F4-7C3464004E35/Event/p10>",
"(...and 204 more...)"
);
...
...
...

Does anyone know why this might be happening?