JavaScript error using attachement uploader

I have installed the Showcase addon and I am getting an error when I try to upload an attachment to an item.

This is the error as shown in Chrome developer console

Code:

:root #content > #right > .dose > .dosesingle,
:root #content > #center > .dose > .dosesingle,
:root #header + #content > #left > #rlblock_left
{display:none !important;}{"attachment_id":1951,"attach_date":1470007623,"filename":"ColemanHeadlamp.jpg","thumbnailUrl":"data\/showcase\/1\/1959-a2faf3181f3d207228c37f02ebd91cea.jpg","deleteUrl":"attachments\/colemanheadlamp-jpg.1951\/delete?temp_hash=0693c51be43ab609683df6f19d24c24a","viewUrl":"attachments\/colemanheadlamp-jpg.1951\/?temp_hash=0693c51be43ab609683df6f19d24c24a","templateHtml":"\n\n<li id=\"attachment1951\"\n\tclass=\"AttachedFile AttachedImage secondaryContent\">\n\n\t<div class=\"Thumbnail\">\n\t\t\n\t\t\t<a href=\"attachments\/colemanheadlamp-jpg.1951\/?temp_hash=0693c51be43ab609683df6f19d24c24a\" target=\"_blank\"\n\t\t\t\tdata-attachmentId=\"1951\"\n\t\t\t\tclass=\"_not_LbTrigger\" data-href=\"misc\/lightbox\"><img\n\t\t\t\tsrc=\"data\/showcase\/1\/1959-a2faf3181f3d207228c37f02ebd91cea.jpg\" alt=\"ColemanHeadlamp.jpg\"\n\t\t\t\tclass=\"_not_LbImage\" data-src=\"attachments\/colemanheadlamp-jpg.1951\/?embedded=1&amp;temp_hash=0693c51be43ab609683df6f19d24c24a\" \/><\/a>\n\t\t\n\t<\/div>\n\n\t<div class=\"AttachmentText\">\n\t\t<div class=\"Filename\"><a href=\"attachments\/colemanheadlamp-jpg.1951\/?temp_hash=0693c51be43ab609683df6f19d24c24a\" target=\"_blank\">ColemanHeadlamp.jpg<\/a><\/div>\n\t\t\n\t\t\n\t\t\t<noscript>\n\t\t\t\t<a href=\"showcase\/attachment\/colemanheadlamp-jpg.1951\/delete\" target=\"_blank\" class=\"button Smallbutton\">Delete<\/a>\n\t\t\t<\/noscript>\n\t\t\t\n\t\t\t\n\t\t\t\t<div class=\"label JsOnly\">Insert:<\/div>\n\t\t\t\n\t\t\t\n\t\t\t<div class=\"controls JsOnly\">\t\t\t\t\n\t\t\t\t<input type=\"button\" value=\"Delete\" class=\"button smallButton AttachmentDeleter\" data-href=\"showcase\/attachment\/colemanheadlamp-jpg.1951\/delete\" \/>\n\n\t\t\t\t\n\t\t\t\t\t<input type=\"button\" name=\"thumb\" value=\"Thumbnail\" class=\"button smallButton AttachmentInserter\" \/>\n\t\t\t\t\t<input type=\"button\" name=\"image\" value=\"Full Image\" class=\"button smallButton AttachmentInserter\" \/>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\n\t<\/div>\n<\/li>","message":"Upload completed successfully","key":"","_visitor_conversationsUnread":"0","_visitor_alertsUnread":"5"}

Also, the image seems to get sucessfully uploaded but the page doesn't indicate that it has been until I save and then I see the image show up for the item. But it doesn't show as an attachment when I am editing it just disappears after uploading without giving an error.

 

Yes, it is happening here too but I found out that the problem is related to the Chrome extension uBlock origin, the thing is, it doesn't report blocking anything for the pages I am getting problems on. But I guess that is an XF thing and not Showcase because it is happening for regular threads too.