What is the \1 for?
Trying to repeat A? So you are searching for A\nA, is that correct?
I don't think you can use \1 to include a \n with TextPad RegEx.
\(A\)\n
works OK by itself. Finds three lines unless you select to match case, and then it only finds 2 lines, just as it should.
If I use \1 as replacement for A\n, it works OK, I end up with AA\n, but it does not translate correctly in the search mode. Expression \1 cannot be found.