Error EC8F17B7 has actually been fixed in Backup Exec System Restore 8.5.5, however you can get your incremental backup working by disabling Search engine support for Google Desktop and Backup Exec Retrieve.
To disable Search engine support for Google Desktop and Backup Exec Retrieve, edit the backup job and deselect Enable search engine support for Google Desktop and Backup Exec Retrieve.
You will now no longer get the E0BB0191 error and your incremental backup should work.