As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT OUT OF FRA - RT IDG DRIVE LIGHT CAME ON STEADY. APU STARTED AND RT IDG DISCONNECTED. APPROXIMATELY 1 HR LATER - APU OIL QTY - EICAS STATUS MSG. APPROXIMATELY 45 MINUTES LATER - APU AUTO SHUTDOWN. FLIGHT DIVERTED TO SNN. REPLACED RT IDG.