TinyMCE on-page editing rendering problem in Web Forms

Description

Steps to reproduce:

1. Setup an Alloy Web Forms site
2. In edit view, open the Alloy Plan page in on-page edit view.
3. Edit the MainBody and then click with the mouse outside the overlay. Make sure the overlay becomes inactive before autosaving.

Actual result: 

The text in MainBody is not similar to the edited one.

Expected result:

The MainBody should be correctly rendered.