It Was Just a Glitch
The last test of the missile defense system didn't work because the attack vehicle didn't launch. The Air Force general in charge said the problem was a minor software glitch
It turns out the software monitors for errors and communications "drop-outs" during the launch cycle and aborts the launch if there are too many errors. The "fix" was to increase the number of permitted errors.
Let's not find out why there are so many errors, errors that might make life exciting for airline passengers, because the data being sent to the attack vehicle before launch are the target tracking data, we'll just let the vehicle launch with even less information than before.
This is so typical: our missile can't pass when a "C" is 70%, so we'll make a "C" 50%.
No Obscenely Expensive Defense Project Left Behind.