Given this small test file, which has 5 blank lines before its two chapter headings, the output from PPtxt contains the following section:
----- spacing pattern ---------------------------------------------------------
0
6 52
15 52
It is correctly reporting that the line spacing pattern is 5, then 2, for each chapter. The "5" on the second line of output is highlighted as incorrect, but the "5" on the last line is not highlighted.
Apparently, this bug was in a previous python version of PPtxt too. I'm not sure if there are any similar situations where the last occurrence of an error is not highlighted correctly.