Your problem comes from the concept of proximity. The description says that we sould return the pair with the lowest last element's index. It means that in [10, 5, 2, 3, 7, 5] the answer is [3,7]. In [10, 5, 2, 3, 5, 7] the answer is [5,5] because the last 5 has an index lower than 7.

works perfectly fine for me (python) !

You should say what is the language you work on.