I did a lot of work with ruggedized Windows Mobile devices for field service workers. After one update, we noticed that data was being entered incorrectly more often than usual and the office workers had to correct it a lot more often.

We couldn’t find the issue for the life of us. Eventually, we sent someone down to the shop to see what was happening. We realized that the field workers weren’t waiting for the screen to update and were tabbing through using muscle memory. I had inadvertently switched a field and the tab order around.

And then there was the time that a new user was complaining about not being able to see a field but all of the old repairmen didn’t complain. Someone hadn’t actually tested the colors on the screen outside in direct sunlight where everyone was working. The new screen was just like the old one and all of the other repairmen just did it by memory.