Long time lurker. Have been following this thread and thanks all for your thoughts.
A crazy idea: Could a APU mount failure failure due to improper maintenance, loose structure (eg APU) and resonance vibrations jam and break the rudder, leading to the tail coming off?
This happened to Partnair Flight 394 in 1989, leading to the tail coming off and midair disintegration.
https://en.wikipedia.org/wiki/Partnair_Flight_394