I thought I had this resolved earlier, but back to the same issue.
I have found that if I include any src= file (whether external or saved within my own directory structure) in a metabox for the edit-form-advanced.php via a plugin, the encoding becomes disrupted such that a dash ("-") becomes "â€”" in the tinyMCE editor window (same is true if I switch to the "HTML" view. I have no idea why or how to fix it.
In this case, I have an file which I have "required" in many different ways (as a .js, .php, and .html file) and regardless of how I require it, it still disrupts the encoding as mentioned above.
An image of this can be found here:
Here is the entire file's content... (very simple jQuery example):
In the plugin file that creates the metaboxes in the editor I simply have...
Any thoughts anyone may have would be greatly appreciated.
Thanks so much!!