Thanks for the comments and your i18n-tasks gem!

Sounds like a great idea. Would definitely have to follow an Outlook Calendar style functionality where a single occurrence could be edited of a series. Worth looking into.

From a UX perspective, it is consistent with how, by default, other forms work. You're able to refresh the browser or hit the back button to navigate away from normal forms without warning and losing any field changes.

My approach is usually to provide some form validations via javascript. So if the user adds a record or if they modify existing fields on the page, set a variable in JS. If the user navigates away from the page before saving, then show them an alert to prevent leaving the page on accident.

Are you entering the iframe code in the "code view", using the Video button or are you pasting it into the WYSIWYG editor? 

Also, can you share the snippet that you're using to display the content of the editor? For example, do you have a <%= raw @model.content %> or something similar?

Error 500 indicates that something went wrong on the server side and it should have logged something into your application logs. Check there and if you're unable to figure it out, post the relevant section of the log please.