CAL-DAV-Synchronizer bricht ab

Hey ihr Lieben,
bei der EInrichtung meines mailbox.org-Kontos hätte ich gern meine bislang in Outlook 2019 (auf Win11) in einer Offline-pst gepflegten Kalendereinträge in den mailbox-org-Kalender übertragen. Ich hatte dazu den CAL DAV-Synchronizer versucht, der hat seine Arbeit jedoch erfolglos beendet (Log-Schnipsel unten).

Hat jemand eine Idee, woran das liegen könnte bzw. insbesondere, wie ich das beheben könnte?
Gibt es eine andere Idee, wie ich das eigentliche Ziel erreichen könnte?

Export der Kalendereinträge in eine ics-Datei hatte ich versucht, die wollte ich in Thunderbird importieren und so die Synchronisation mit mailbox.org erreichen. Der Import in Thunderbird hat sich allerdings auch aufgehangen.

Hier das Log von CAL DAV Synch:

CalDavSynchronizer.DataAccess.WebDavClientException: Response status code does not indicate success: '400' ('Bad Request'). Message:

at CalDavSynchronizer.DataAccess.HttpClientBasedClient.WebDavClient.<EnsureSuccessStatusCode>d__10.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)

at CalDavSynchronizer.DataAccess.HttpClientBasedClient.WebDavClient.<ExecuteWebDavRequest>d__9.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at CalDavSynchronizer.DataAccess.HttpClientBasedClient.WebDavClient.<ExecuteWebDavRequestAndReadResponse>d__7.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at CalDavSynchronizer.DataAccess.CalDavDataAccess.<GetVersions>d__29.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

at CalDavSynchronizer.DataAccess.CalDavDataAccess.<GetVersions>d__29.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at CalDavSynchronizer.Implementation.CalDavRepository`1.<GetAllVersions>d__9.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at GenSync.EntityRepositories.VersionAwareToStateAwareEntityRepositoryAdapter`4.<GetFullRepositoryState>d__5.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)

at GenSync.Synchronization.Synchronizer`11.<Synchronize>d__27.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at GenSync.Synchronization.ContextCreatingSynchronizerDecorator`7.<Synchronize>d__3.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at CalDavSynchronizer.Scheduling.SynchronizationProfileRunner.<RunAndRescheduleNoThrow>d__22.MoveNext()