Async restore and multiple web+cron servers

We have 4 web servers that all also run cron every minute, and we recently enabled async backup/restore on our site. When a user attempted to restore a course, the uploaded MBZ file was on server 3 but the cron job on server 1 picked it up and errored out because the MBZ file was in a temp directory on server 3. Are there configuration options that we are missing?