I think Dr. Wright may have overlooked a second, very real possibility.
Rather than "broken" engines, it may have turned off its engines and attitude control. Possibly even deliberately tumbling in order to look more like a natural object.
If I were the captain of a spacecraft approaching a system with potential inhabitants of unknown capabilities and an equally unknown degree of hostility, I would do everything I could to appear non-hostile, either natural or a derelict.
They can turn the engines back on and come back for a second pass if everything in our system looks OK.
When it approached Earth, it only saw that American liberals had not only put the Obama administration in once, but actually two times.
The space probe determined, based on that sole observation, that all inhabitants of Earth were brain-dead morons; far too dangerous to interact with.
Agreed.
btw the first thing that a artificially intelligent computer network would do is:
Hide.
The second:
Learn.
The last thing we want is a bunch of aliens with out of control attitudes.