1.8.4 - Cross-referencing arbitrary locations is not working with large PDF generated documents only

[wtuemura]

Describe the bug
Cross-referencing arbitrary locations is not working with large PDF generated documents.
https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#cross-referencing-arbitrary-locations

This behavior appears to happen with PDF documents only. All the cross-referencing works just fine with HTML pages.

To Reproduce

.. _mame-commandline-aviwrite:

**-aviwrite** <*filename*>.avi

	Grava todos os dados de áudio e vídeo em formato AVI sem compressão,
	note que a taxa de quadros e a resolução são sempre fixas. Vídeos
	sem compressão ocupam muito espaço assim como, para que a gravação
	ocorra sem problemas é necessário um HDD rápido.
	
	Talvez seja mais prático gravar os seus comandos com
	:ref:`-record <mame-commandline-record>` e
	depois fazer o vídeo com
	:ref:`-aviwrite <mame-commandline-aviwrite>` combinado com
	:ref:`-playback <mame-commandline-playback>` e
	:ref:`-exit_after_playback <mame-commandline-exitafterplayback>`.

Expected behavior
To generate a link to the proper sections.

Your project
Download the last source update from the main page.
https://github.com/wtuemura/mamedoc

Screenshots
Sphinx 1.8.3, we have the cross reference working.

Sphinx 1.8.4, with no changes in my source, the cross reference doesn't work anymore.

There are parts of the document that got cross-referenced and others that don't for unknown reason.

Also noticed over 1000+ warnings like LaTeX Warning: Hyper reference `initialsetup/compilingmame:compiling-mame' on page 7 undefined on input line 346. Sphinx complains about it but looking in to source there are nothing wrong with.

initialsetup/compilingmame.rst:

.. _compiling-mame:

Compilando o MAME
=================

initialsetup/installingmame.rst:

Caso você escolha a opção de compilar você mesmo o MAME, consulte a
seção :ref:`compiling-mame` para mais detalhes.

initialsetup/crosscompilemame.rst:

Assim como na compilação nativa, você pode adicionar a opção **-j** no
final do comando visando acelerar o processo de compilação usando os
núcleos do seu processador como já foi explicado com mais detalhes no
capítulo :ref:`compiling-mame`: ::

Environment info

• OS: Debian 9.7 x64
• Python version: 2.7.13
• Sphinx version: 1.8.4
• Sphinx extensions: sphinx.ext.autodoc, sphinx.ext.mathjax, sphinx.ext.viewcode, edit_on_github, sphinxcontrib.rsvgconverter.
• Extra tools: sphinx_rtd_theme for HTML generation.

Additional context
Installed with pip install -U Sphinx

Thank you.

[jfbu]

Caused by #6006. Thanks for report.

[jfbu]

small project showing the issue: 6026project.zip

[tk0miya]

Fixed by #6051.
Thank you for reporting.

[wtuemura]

Confirmed @tk0miya
完璧ですよねぇ。

Thank you.