My business cards slide around in the printer tray of my Signature IV/Pro/Z6.
1. Make sure you have the correct size business cards. The correct size is:
Business Card = 59mm X 85mm
2 . Also make sure you are using the business card adapter kit which comes with a special template to hold the business card steady in the printer tray.
3. Finally, be sure you are doing the printing separately from the burning, otherwise the robotic arm will improperly place the business card disc into the printer tray.