@danluu
Chain....weakest link.
In my experience once the car gets delivered to the car yard we enter the stage where no matter what happens absolutely no one there will be able to:
1. Fix it
2. Fix it.
Having an upgrade that fails and gives an answer like this is unacceptable. Having an upgrade that depends on a programmer being available is not a good business result.

More testing needed. (Repeat as necessary)