The local mechanics couldn’t figure it out, so this team was assembled from the mechanics at headquarters to fix the plane.
They inspected the plane and found no damage. They had the pilots make multiple test flights - they could not reproduce the problem. The pilots were adamant that the plane was broken. Engineers from Airbus ended up flying out to assist. They couldn’t identify any problems.
After a few months of effort and a lot of very expensive dart throwing and parts swapping, they gave up. As far as anyone could tell, there was never anything wrong with the plane, and based on comments overheard from the pilots, they simply did not like this particular plane. It had been pulled from a boneyard and recertified, and they considered flying it beneath them.
FIL did come home with some cuban cigars and really high quality counterfeit Fluke multimeters he got from the local market, though.