constraint error

One of the Outlook365 calendars that is shared by a colleague returns this error on every synchronization call:

Constraint

Action: ReceiveCalendar
Calendar: Person's Name

SQLite.SQLiteException: Constraint
at SQLite.PreparedSqlLiteInsertCommand.ExecuteNonQuery (System.Object[] source) [0x00178] in <84b9c9e630fa45bd8ac799333976ebbf>:0
at SQLite.SQLiteConnection.Insert (System.Object obj, System.String extra, System.Type objType) [0x000ef] in <84b9c9e630fa45bd8ac799333976ebbf>:0
at SQLite.SQLiteConnection.Insert (System.Object obj) [0x00012] in <84b9c9e630fa45bd8ac799333976ebbf>:0
at XCalendarApp.SQLite.Repositories.RepositoryBase`1[T].Insert (T entity) [0x00006] in <5a6eda7644914328b00993b248c6cc0a>:0
at XCalendarApp.SQLite.Repositories.CIExpandedRepository.Insert (XCalendarApp.SQLite.Entities.CIExpandedDataEntity entity) [0x00025] in <5a6eda7644914328b00993b248c6cc0a>:0
at XCalendarApp.ProviderBase.StorageManager`8[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData].AddCIExpanded (XCalendarApp.SQLite.Transaction transaction, XCalendarApp.Model.Data.ICalendarItem calendarItem, XCalendarApp.Common.Timezones.TZDateTime tzStartDateTime, XCalendarApp.Common.Timezones.TZDateTime tzEndDateTime) [0x0008b] in <d1275c79399f4afd9057082e36313d21>:0
at XCalendarApp.ProviderBase.StorageManager`8[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData].AddCIExpanded (XCalendarApp.SQLite.Transaction transaction, XCalendarApp.Model.Data.IAppointment appointment) [0x0000f] in <d1275c79399f4afd9057082e36313d21>:0
at XCalendarApp.ProviderBase.AccountProviderBase`9[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData,TAccountOptions].UpdateExpandedDataForAppointment (XCalendarApp.SQLite.Transaction trans, TCachedAppointment appointment) [0x0009b] in <d1275c79399f4afd9057082e36313d21>:0
at XCalendarApp.ProviderBase.AccountProviderBase`9[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData,TAccountOptions].UpdateAppointmentAndExpanded (XCalendarApp.SQLite.Transaction trans, TCachedAppointment appointment) [0x0004b] in <d1275c79399f4afd9057082e36313d21>:0
at XCalendarApp.MicrosoftProvider.MicrosoftAccount.SyncReceiveCalendarFromProvider (XCalendarApp.MicrosoftProvider.CachedMicrosoftCalendar cachedMicrosoftCalendar, XCalendarApp.Model.Data.SyncResults.SyncResult syncResult) [0x004d6] in <e8542ae201a14b9a9ffb0e0183411c23>:0
at XCalendarApp.ProviderBase.AccountProviderBase`9[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData,TAccountOptions].SyncReceiveCalendar (TCachedCalendar calendar, XCalendarApp.Model.SyncReason syncReason) [0x0011f] in <d1275c79399f4afd9057082e36313d21>:0

I can still see this person’s calendar.  Other Outlook365 calendars shared with me do not produce this error.

Thanks in advance for your help.