Final Layout being wiped out when editing text field in Sitecore 8.1
<p>I have a strange issue whereby when I edit a rich text field in the experience editor and save the page, it takes me to the layout not found page.</p>

<p>When switching back to the content editor, I can see that final layout has been completely wiped (the shared remains intact). I've noticed that if I change to the shared layout within the experience editor (via the presentation tab) and perform the same edit - it works fine.</p>

<p>What would cause the final layout to be wiped?</p>