I have had a similar issue before and it was because of the browser caching the rich text editor.
One of things you could do is wipe the cache and then refresh and I bet it will fix your problems. You may also want to put cache busting code on that page so it can load any element from cache.
Sometimes, I found a "hard" refresh will do the trick as well by pressing F5 - but I would look into non-cache code for the page to ensure your users won't have any issues - unless it is just for a back-end that you control. If that's the case, just clear the cache and reload the page.