If left un-capped, the accessory port on both the Alpha and Bravo can introduce an air leak into the body of the manipulator. Ensure that the arm is not left for a long period without either the accessory port blank or a camera mount installed, otherwise you may find that leak warnings pop up in Reach Control and the arm is no longer under vacuum.
If you have left the accessory port un-capped and are getting a leak warning, use the appropriate Service Kit (RA-1065 for Alpha or RB-1090 for Bravo) to repull vacuum in the joint through the port. Contact Reach Robotics Sales if you need a quote for a Service Kit.