I have found the same problem, however making a change in the HTML tab, does show itself on the preview page. So it’s only on changes done in the visual tab that does not work for me..
I’m using the Mobile Device Detect Reloaded plugin with same result. Other forum posts suggests this to be a core problem after 3.2.x .. I’m running 3.2.1.
Seem to have the same problem, and a suggested fix from a different thread regarding removing the * required portion of the field element [field* fieldname] did not work..