When setting up the Buzzsaw Vault file sync, make sure that the user you have chosen as the login for the Project Sync Settings has appropriate security rights for the files being transferred. We had added an explicit username whose sole purpose is to handle the syncing, even though the user had full R/W/D rights to the entire Vault, in the case where certain files took on 'Security Override settings' as they passed to different states, the username had to be added to the Groups associated with those security settings to allow new files in Buzzsaw to overwrite those in Vault.