We have exactly this situation. Did anyone find a solution?
Symptoms: initially had the "blank $wgScriptPath" problem, which we fixed as per
https://github.com/pediapress/Collection/commit/bf83e7689f76a47802ace1266832ee93d8efc2cdNow we get a PDF download but that download has nothing except standard headings, eg. a download for a single page just has a page header, page number, and "Article Sources and Contributors" and "License" headings. A download for a book that I created has the title page, table of contents, chapter headings, and the "Article Sources and Contributors" and "License" headings -- but no actual content!
I agree with the previous poster's suggestion that this might be related to the $wgScriptPath problem. For instance, it might have something to do with this:
$ grep wgScriptPath Collection.templates.php
$mediapath = $GLOBALS['wgScriptPath'] . '/extensions/Collection/images/';
global $wgScript, $wgScriptPath;
$mediapath = $wgScriptPath . '/extensions/Collection/images/';
$mediapath = $GLOBALS['wgScriptPath'] . '/extensions/Collection/images/';
I'm going to try and find a workaround similar to the one applied to Collection.body.php and see what I get out of it.
A.