It is surprising how pilots can think that they checked something.
A certain large operator of the Bae 146 had an aircraft returned to service from maintenance with the roll spoiler indicators cross wired.
Fortunately the spoilers worked in the correct sense (not easily seen from the cockpit) but for about a month every day, every sector, the crew
diligently did their control checks without picking up Engineering's "deliberate" error.
That is not one crew, but probably a dozen or more who would have flown the aircraft in that time.