Has anyone else suffered this (or similar)…
You have an Ephox field with several inline variants. Seemingly inexplicably (meaning I can never tie this down to adding or removing any other variants/editing the field in any other way etc…) they will cease to prieview.
Adding a new variant or deleting and reinserting one of the existing ones usually fixes the problem and they prieview again.
If the page gets redrafted and republished while it is broken the variants disappear from the live site.