Apparently Symfony doesn't add a _route parameter to subrequests (esi render call) so PropelParamConverter throw an error accessing getOption method on not-existent object on line 98.
The following notice was triggered:
Runtime Notice: Only variables should be passed by reference in
/home/vagrant/www/project/vendor/propel/propel-bundle/Propel/PropelBundle/Request/ParamConverter/PropelParamConverter.php
line 193
enhance the pk handling to use the real PK name and not only 'id',
fix new sensioFrameworkBundle 2.1 requirement:
ParamConverterInterface::apply() method now must return a Boolean value indicating if a conversion was done
Currently, parameters like "author_slug" are translated by the param
converter to a "->filterByAuthor_slug()" call. I changed this behavior
and they are now translated to "->filterByAuthorSlug()".