Only 8 clashes for me as well...
Is the modified entry at 10 across a word? I can't find it in Chambers
I think there's a flaw that results in ambiguity in the final result:
Note that there is nothing in the instruction to rule out additional clashes in deploying the letters from the 7x4 block (in fact there a definite clashes between the original unches and the final ones). That means that it would be legitimate to switch whatever you put in the last row with the unchecked letter in any of the ???????? ones (for example the last two letters of 27 down). We are changing a bunch of unches in the two replaced entries, after all, so why not change the ones from the ?????????
Note by Admin - words removed as I am informed that they give away how some answers are to be treated prior to entry.