[fingers]

Hi, sorry to hear about your troubles.

If something in the drivetrain, either in the gear box, transfer unit or diff had broken and then generated enough heat to weld itself to something else, then no it wouldn't have thought it would drive as sweet as a nut. I would seek advise from a Mitsubushi before you decide anything, if you can take them and show them the broken/damaged parts. If the Mitsie garage says you would have noticed this fault if you drove with it, I would then notify the guy doing the work and then if needed, seek legal advise.