It causes an always loading error on a clean environment right after the installation when the button just keeps loading – see the screenshot – http://take.ms/s4HHb
I am not sure how it works on the demo environment and with everyone else but doesn’t work on a clean and fresh installation. So I share the solution here and I think it would be great for the devs to comment.

My programmer friend has fixed the issue and I just thought you might want to fix it for the other customers as well.
And should you have any tasks like that, I can share his contact details =)
So what he did is:

replaced in this
foreach (array_diff($this->engine->getOcDocument()->getScripts(), $this->document_scripts_before_render) as $script)
with
foreach (array_merge($this->engine->getOcDocument()->getScripts(), $this->document_scripts_before_render) as $script)

in this file
system/vendor/BurnEngine/library/OutputHandler.php