We'll check and get back to you soon. 

I googled the error and I have the exact same issue. 

For me it appears when editing a post via the frontend. I have an ACF system to handle frontend submission/edit of posts and it appears in the TinyMCE window and on the side of the screen. See attached image.

Apparently this only happens on pages and posts with WYSIWYG editors. I've tried disabling all sorts of plugins that have something to do with said editors but even rolling back wpDiscuz to an older version didn't help.

I'm facing the same issue suddenly. 

The front-end content editor shows Failed to initialize plugin: wpDiscuz - every time it is even refreshed.

Dear users,

We don't find such an issue on our test websites. Could you please send the admin login details to info[at]gvectors.com email address? I'll ask the developers to check the issue for you.

Please let us know once the email is sent. 

I have the same problem. Please do let us know here if you find a solution. Thank you

By the way, in my case, the problem is coming from wpdiscuz-shortcode-tinymce.js, these lines..

image: wpdObject.image,
tooltip: wpdObject.tooltip,

$('#wpd-inline-content').html(text ? text : '<span class="wpd-text-error">' + wpdObject.no_text_selected + '</span>');
tb_show(wpdObject.popup_title, '#TB_inline?width=' + W + '&height=400&inlineId=wpdiscuz_feedback_dialog');

wpdObject not initialized ( You can inspect and check if it is the same for you)

FYI..