An error occurred while pre-processing the request submitted by the host... (Rich Text Editor)

In RTE (Rich Text Editor), I pasted the page from the other page to replace the existing info and hit saved. I saw the error message but only like half a second before the RTE dialog closed. It wasn’t saved successfully. I wasn’t able to screen captured either b/c it was too quick. I managed to do screencast and saved that screenshot.

I think we need to improve this error message by appearing in another dialog window above the RTE dialog… that will be easier.

Here’s screenshot. I already solved the errors.

Here’s the short clip