Sort isn't working correctly
 

The cells in col A and in col B contain identical data.
All cells in both columns have a "General" format.
Both columns are unsorted.

I highlight col A and use DATA/SORT/SORT BY COLUMN A/SORT ON VALUES/ORDER A to Z and click OK.

I highlight col B and use DATA/SORT/SORT BY COLUMN B/SORT ON VALUES/ORDER A to Z and click OK.

I expect the cells in both columns to be sorted in the same order but they aren't. (For example: 2008-ITALY001.jpg is in A137 and in B61).

Why isn't sort working correctly?