Intermittant printing delays

One of my customers is using a serial text printer (Card Embossing Machine). It had previously been connected using an ASCII terminal server. They have upgraded their system and eliminated this old terminal server. They are now using an HP JET DIRECT print server. They are experiencing intermittent delays in printing(sometimes as much as 15 minutes). This is in the Admitting Dept. at a local hospital and is causing serious problems for their staff and patients. Any suggestions?