Calendar Repair Assistant (CRA) in Office 365 may have adverse impact on meetings and recurring meetings after migrations. It is recommended that CRA be disabled during the start of any (sync job) migration. This service may be enabled after the migration has been successfully concluded and the end-user has been cutover to the destination. There is no known negative impact when Calendar Assistant is disabled temporarily.
Use PowerShell (PS) to create a remote session to Office 365 tenant then execute the following commands:
Get-Mailbox -ResultSize unlimited | Set-Mailbox -CalendarRepairDisabled $true
The Calendar Assistant is now disabled for all mailboxes in the Office 365 tenant. It can be enabled again by using this PS command:
Get-Mailbox -ResultSize unlimited | Set-Mailbox -CalendarRepairDisabled $false