If you are running lamassu-server versions between 2.0.0 and 2.2.9, you should update to the latest stable version.
Recently discovered was a rare potential for a transaction to be sent twice, due to an interplay between the dropped transaction resending feature and the database. Updating to the latest version patches this.
To display your current version, in your server's terminal run:
npm -g ls lamassu-server
To update your server software, all machines paired to it must first be updated to the latest stable machine softwar. Contact us at email@example.com to request we verify your machine version and/or update it.
After a machine update, follow the article 'Updating your server and admin' to move to the latest stable versions.