Somewhere around 1983.
In real life there were a number of flap track failures occurring at around that time to the earlier 747-100s. It certainly happened to BA and also I think to TWA and PanAm. The fix was to replace the flap tracks with the stronger ones used on the -200s. The cause was minute corrosion pits in the holes through which bolts attached the flap tracks to the main wing structure. Regular inspections were required until these tracks were replaced. As far as I know it never happened on a CofA test flight but it certainly did on passenger service. All cases landed safely but with a goodly amount of aileron and rudder applied to keep straight until landing.