For over two thousand years, engineers had to contend with manufacturing issues. We're still doing that today...
"... its design conception exceeded the engineering precision of its manufacture by a wide margin—with considerable cumulative inaccuracies in the gear trains, which would have cancelled out many of the subtle anomalies built into its design."
From the Wikipedia page "Antikythera mechanism," Google's feature for today, 2017-05-17.
https://en.wikipedia.org/wiki/Antikythera_mechanism
