I had the same issue with html forms that use asp.net code. What I had to do is put that kind of information in a seperate text box. This way ephox validator doesn’t get called. Ephox will try to make it ephox xhtml compliant…even though what you have is. It’s a very buggy wysiwyg.
Yeah, I’ve wrestled with Ephox on many other things similar. Unfortunately this time around the field is just plain text and it’s still editing the code.