Can't erase Headers with Regex

[Ivan_Z]

Hello. I'm new to this so I might be making some mistakes here but I'm trying to delete the headers of a PDF while converting it to MOBI.
In Search & Replace I'm searching for the following expression with no quote marks:
"<a id="p[0-9]+"></a>[0-9]+<br>Introduction<br>"

Calibre shows me there are 3 instances of this.

For replacement text I use blank or "", I have tried both.
I then Add it to the list.

When I convert the book the header is there in the middle of the text together with the page number.

Am I missing a step here? What should I use as replacement text to erase it?

Thanks.

EDIT: Just realized there is a conversion subforum a bit down, sorry about posting in the wrong section.

[kovidgoyal]

https://www.mobileread.com/forums/sh...d.php?t=186697

[Ivan_Z]

Thanks for the link, everything requested is attached.
I created a sample from the actual PDF and now the "Introduction" expression is working, but there is a second one still not working. That expression is:
"<a id="p[0-9]+"></a>[0-9]+<br> T h e G r e a t G a m b l e<br>"
So both examples can be used to detect the problem.

Options different from default are:
Heuristic processing enabled.
In page setup, Kindle is selected.
In PDF Input, no image is selected.

Thanks.

[kovidgoyal]

That's because the spaces are represented as entities in the actual HTML produced by the input plugin. I will add some code to replace those in the next release.