Mailbox Export Request and MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003)

As I was preparing to export several mailboxes to PST for a Cross Forest Exchange 2010 to 2016 Migration as a part of an acquisition, I ran in to an issue that when I would run a New-MailboxExportRequest and get an error "Couldn't connect to the source mailbox" When running the cmdlet with a -Verbose, would see the error "MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003)" After going through some troubleshooting steps:
-Verifying MAPI is enabled on the accounts.
-Verifying that the Exchange Trusted SubSystems group had R/W Share Permissions.
-tried a different users.

After nothing fixed my issue, I called support. One troubleshooting step that they had me do that never crossed my mind was to create a new mailbox database. after doing that I moved a user successfully to that database and was able to export it with no issues. upon comparing the mailbox database settings Get-MailboxDatabase -Identity I noticed that the new database did not have a Public folder configured and the other database did but it looked as if someone had deleted it. Using ADSI we removed the Public folder path from the database and were able to export mailboxes without any issues.

Removing Public Folder path from Mailbox Database:
1. Launch ADSI and enter the configuration Node.
2. Navigate to :
Services > Microsoft Exchange > Exchange OrgID > Administrative Groups > Exchange Administrative Groups (FYDIBOHF23SPDLT) > Databases
3. Right-Click the Database with the public folder you want to remove and click Properties
4. From the Attribute Editor tab select the attribute msExchHomePublicMDB
5. Click Edit
6. Copy that value to a text file as a backup. :)
7. Click Clear
8. Click OK
9. Click OK to close the attribute editor
10. Close ADSI Edit