Media inserted does not appear within post content after publish

Hello,

I am trying to setup a simple front end form to submit a post, and allow users to insert media into their post content. Problem I am having is that while I can insert media (using the tinymce) while using the form. Once it’s submitted and I view the post, the media or links to the media simply don’t display. I did initially try the ‘media_buttons’ method, but they didn’t respond at all in the front end.

I only just updated to WordPress 4.9.4 (previously 4.7.9) both with the same result.

Any direction on this would be greatly appreciated.
Thanks