I struggled with this for hours, and I hope it’s not too late to help.
But, I found the solution: I designed a template using the drag-drop feature and then exported it. I then created a new template and pasted the exported template code.
Editing the main copy div to add mc:edit="main"
I just noticed the same issue.
Here is a fix I came up with. Had to do a string replace.
<title><?php echo str_replace('Product Categories |', '', wp_title('|', false, 'right')); ?><?php bloginfo('name'); ?></title>
