From checking letters it seems the method of entry is to take a surplus letter from the long answers and transfer to the short - 2 of each in each set. I have run into problems where the surplus letters are in unchecked cells, eg in Set 6. This has led to transferring from unchecked cell to unchecked cell in eg 37 across to 17 across (Set 2) and therefore not a unique solution. Where have I gone wrong?