Delta 138 diversion

On June 1, Delta 138 from Atlanta to Athens, Greece was diverted to Halifax, Nova Scotia a little over 3 hours into the flight. The tracking map showed the change in course, and the path appeared to be very erratic, including several sharp turns. The plane made a rapid descent from 31,000 to 8,000 feet over about 4 minutes, and the Delta online tracking map was taken down with a statement that flight information was no longer available. The plane finally landed, and Delta dispatched another plane from Atlanta to pick up the passengers. They arrived in Athens about 6 hours late. Does anyone know what happened? How can I find out?

flightaware.com/live/flight/DAL1 … /KATL/CYYT

DAL138, Boeing 767-300, enroute from Atlanta (KATL) to Athens (LGAV), requested clearance to divert to St. John’s (CYYT) due to a malfunctioning engine valve. No emergency was declared and no assistance was required. The flight dumped fuel from position 445840/595333 to 453914/582211 from 23:44Z to 23:52Z. There was minimal impact on operations.

Source: CADORS