I cannot recall ever hearing of the cited hardware fault (accessory gearbox dying...) in flight, unless caused by some considerable external event (I recall one hit by a thrown fan blade from the opposite engine...)
However, I know a test crew who attempted to start a preserved engine, and when it finally lit off, a tailpipe fire (preservative oil) ensued. The throttle jock panicked, re-engaged the starter during coastdown, and was unable to restart the engine.
Upon hitting the starter, N2 took off pretty quickly, oil pressure indicated OK, but fuel flow remained very low, no EGT, no N1, ...
We found the "tower shaft" was sheared from the starter impact torque - a very clean break. The starter would turn the gearbox, pumps, etc. BUT no drive available to the core engine! I rewrote the engine fault isolation book to cover this event.