Links in blog posts not rendering (markitup, textile)

Update: The system will only render the link if the https:// is not present in that string. So textile code "text":https://www.test.com won't render the link, but "text":www.test.com will. Of course this means the link won't work correctly due to pathing.

In a blog post, when a link is inserted via the markitup toolbar icon, the code inserted is "linktext":https://www.link.com. Upon saving this post and reloading the blog post, the link html does not render. The above markitup template text appears on the page instead.

I've just upgraded a client from 2.5.4 to 2.8.9 hoping that it would resolve the issue, but sadly it remains (the updated markitup folder was copied over as instructed).

The client has used textile formatting for all of their blog post. Switching to markdown, the markdown link code does work, but then every post would have to be manually updated from textile to markdown formatting, which I'd rather avoid.

Post Description template tag

<perch:blog id="postDescHTML" type="textarea" label="Post" order="2" editor="markitup" textile="true" size="xxl autowidth" required="true" />

Diagnostic

Perch: 2.8.9, PHP: 5.3.3, MySQL: 5.0.83, with PDO
Server OS: Linux, apache2handler
Installed apps: content (2.8.9), assets (2.8.9), categories (2.8.9), perch_blog (4.6), perch_backup (1.2)
App runtimes: <?php $apps_list = array( 'content', 'categories', 'perch_blog', ); ?>
PERCH_LOGINPATH: /manage
PERCH_PATH: ***
PERCH_CORE: ***
PERCH_RESFILEPATH: ***
Image manipulation: GD
PHP limits: Max upload 16M, Max POST 16M, Memory: 128M, Total max file upload: 16M
Resource folder writeable: Yes
HTTP_HOST: www.lazer.ie
DOCUMENT_ROOT: ***
REQUEST_URI: /manage/core/settings/diagnostics/
SCRIPT_NAME: /manage/core/settings/diagnostics/index.php