Links in pdf file not working properly

Hello everybody

I'm converting a book I wrote from mobi to pdf with Calibre. While formatting the document, I used some html, including a few links between different parts of the same document.

However, when I test the pdf document and I click on links, they always send me about a page before of what I marked with the a name attribute...

I've been looking around but can't find why. I've checked my book on mobi, and everything is OK there. This only seems to happen on pdf.

Any ideas or explanations?

Thanks!