The embedded player (/engage/ui/embed.html) does display the player preview image if present as the parsing of the attachments in the episode xml is broken.
Specifically the code in embed-hybrid-initialize.js at ln 873 doesn't work as it looks for elements (via jQuery.find()) in the episode XML without specifying the namespace. This is required in Firefox but not Chrome, therefore to work on both:
should change to:
:attachment, attachment').each(function ()