FR24 could be correct, but it could be way off as well. I have seen position shifts and track shifts over Europe many times. It is useful as information only, not proof.
But 0 altitude is 0 altitude, and that is where MH 370 is right now.
A catastrophic failure of some kind. Bomb, terrorist attack or structural failure.
I think they should start looking at the documentation for the wing repair. It would not be the first time a botched repair brought down an airliner, but I'm baffled by the complete lack of communication.
The 777 does send maintenance reports home to base when something goes wrong?