Public Folder - Discovery Issues

Hi, Having an issues with discovering public folders, 
Every other category of the migration has discovered, matched and migrated perfectly, the only issue im having is discovering public folders! 
Unknown error: The SMTP address has no mailbox associated with it. (Microsoft.Exchange.WebServices.Data.ServiceResponseException)
or 
Unknown error: The Id property must be set. (System.ArgumentException)
I cannot seem to get past these two errors, i have granted pretty much every consent in the system as well, updated all the admin UPNs etc. 
Cannot get these to match up 
 
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