Hey there,
I am having the same issue one my site. I just manually injected the tinyMCE code into the page and was able to save my key. The tiny MCE seemed to be completely missing.
https://www.tinymce.com/download/download.php
Download inymce_4.1.7_jquery.zip\tinymce\js\tinymce\tinymce.min.js
Copy and pasted the contents of this file into the js console before pressing save.
Im not sure why the code is not included in the first place. If one so desired, you could include the js file. Maybe wrapping it in something like
if(typeof tinyMCE== "undefined"){
/* Copy code form file here */
}
I haven’t used a form yet, but ill post an update if I run into more issues.
Cheers
kratomone.com