Tech support for factory machines. I used to work in a fairly modern (in terms of products) factory, and the SMT assembly machines were positively archaic. Most were decades old by the time I quit, they all had their own quirks, and very few people who could troubleshoot them. The factory was shut down every weekend, and getting the machines to talk to each other and the server on Monday mornings was a ritual just short of praying to the Omnissiah.