Improvements and increased complexity

Like others, I am glad to read that a big computer problem that interfered with plane travel was not a plot or a result of malicious intent, but was an old fashioned boo-boo, an error.  As we keep researching and trying, nobly, to improve, we do research.  It is careful, arduous research.  We find a way to work better, faster.  An update is sent to all users.  It needs to be conveyed accurately and it needs to be applied.  What could go wrong?