Hi Ken,
This is likely related to an issue with AJAX. Try this:
1. Go to Module Configuration and disable AJAX from form configuration and edit your email content again.
2. If it still does not take, edit the email content once again, but this time, before you hit update, switch the editor from rich-text to basic text then hit update.
That should do it for you. Let us know if the problem persists. Thanks!
Candace