What was found
BEFORE TAKEOFF , CREW WAS ALERTED WITH A WARNING ILLUMINATION, THRUST REVERSER UNLOCKED (RED), ACFT RETURNED TO RAMP. RIGHT UPPER THRUST REVERSER DOOR WAS OPEN, RIGHT LOWER DOOR CLOSED. INSPECTION REVEALED RIGHT UPPER THRUST REVERSER DOOR, ACTUATOR AFT ROD END, WITH SPHERICAL BEARING, EXPERIENCED A MECHANICAL FAILURE. ROD END, PN P3A1700. FURTHER INSPECTION REVEALED THAT THE ROD END SPHERICAL BALL WAS SEIZED, TO ITS EXTERNAL HOUSING, AND THE INSIDE OF THE SPHERICAL BALL WAS SEIZED TO THE DOOR ATTACHMENT BOLT. ROD END COULD NOT BE MOVED IN ANY DIRECTION WITH A HAMMER AND DRIFT.