Error: "Cannot open this item. Unable to open the free/busy information. You do not have sufficie (4332279)

After a migration, opening a shared calendar appointment returns the following error: "Cannot open this item. Unable to open the free/busy information. You do not have sufficient permissions to perform this operation on this object' The user has the correct permissions on the calendar and on the mailbox level.

There are a number of workarounds currently: - Use the Self-Service Desktop Migrator (SSDM). Migrating with this does not return this issue. - Running the following Outlook.exe stiches resolves the issue in some, but not all environments: /cleanfreebusy, /cleanreminders and /resetfolders - Open the calendar from the source user, open the shared permissions dialog, untick, and then re-tick the permission set. So re-setting the permissions will always resolve the issue.

- When migrating with SSDM, it does not return this error and the migration works - Removing the schedule + free/busy folder and re-creating this does not help - A MAPI low level connection works and the user and open the shared user's calendar