[roger64]

I think we do not speak about the same thing. Your plugin checks the ids on both sides. This script checks the chapter numbers on the return side (on the body side they usually all point to the same chapter containing the notes so it's easy to check).

Even if the ids are correct, a wrong chapter number is enough to break the return link. So a safety check of the chapter numbers can confirm you than the links are working both sides. Ids and chapter numbers are the two variable elements of any link.

I asked a friend to write this script because I had to deal with some books with broken links. To put back the missing (or wrong) chapter numbers, I had to do it manually, jumping from one to another or...

I'll show you.