Apple can’t get enough of Mike Janicek. The firm needed him so much that he worked at the tech giant three times over four decades. First, in 1984, he worked as a contractor at an Apple keyboard and mouse factory. The second time, between 2002 and 2009, he supervised the manufacturing of connectors and cases. He rejoined a third time in 2014, when he was 55, to help make the Apple Watch.

Apple managers called him back that last time when they ran into problems automating production of the yet-to-be-released Apple Watch, whose complex machinery was too delicate for human hands to assemble. The high-profile Watch, the first major Apple product since Tim Cook took the helm as CEO, was dogged by delays. It needed the help of a seasoned crew of manufacturing veterans who called themselves the “old dogs.”