This is an old known issue where calendar events cannot be updated post-migration in the Exchange/O365 destination. The actual origin of the issue is unknown.
This issue is not specific to MigrationWiz; it is a defect in Microsoft products. Please refer to the following Microsoft links:
- Outlook, Exchange and Out-of-Date meeting updates that are NOT OUT OF DATE!
- Meeting request is out of date
- Outlook Calendaring Issue : Meeting "Not Current", unable to accept meetingupdates.
- Recurring Meeting "Not Current," unable to accept meeting requests
- "This meeting request was updated after this message was sent"
There are some indications this may be caused by a difference in clock times between the Outlook client and the Exchange server. It may also occur in some scenarios where cell phones update calendar items during synchronization.
This issue has been confirmed to occur with Microsoft migrations as well, using the Microsoft Exchange Mailbox Replication Service (MRS) Proxy service. In fact, there has been an open case where a premier customer who has had this issue using MRS (not MigrationWiz) since May 2014. Microsoft has not yet been able to provide a solution. Based on the information provided in the URLs above, this problem has been randomly affecting users for years.
BitTitan Support investigated the issue in lab environments and, after migration from different versions of Exchange Servers (a plain vanilla Exchange Server without any customization), was unable to reproduce the issue using Outlook. Therefore, if using Outlook and this issue arises, it may be specific to the data migrated, or the environment. In some cases, BitTitan Support has received reports of this issue with OWA, but not Outlook.
The only workaround we've found is to have the organizer recreate the calendar event and send it out to all the recipients.
Follow this search link in Google for more up-to-date information: