Hi, unclued,
The black cells in row 9 from the top, column 4 from the left, and in row 7 from the top, column 12 from the left, which are the middle cells of the horizontal blocks of three adjoining cells, should be respectively in row 7, column 4 and row 9, column 12 in both grids. So in column 4, the top entry has 6 letters rather than 8 and the bottom entry has 8 letters rather than 6, and the other way round for column 12.