I use VEForAll with Page Forms. I have some fields, and a textarea that loads VisualEditor with VEForAll. It happens that the page is "almost" loaded, except the VEForAll part. Then, the textarea is still "blank" (its content is not loaded) and if I click the Save button before I wait the full loading of VEForAll, then the page is saved with this "blank" content. There is loss of data. I think a quick workaround would be to ensure that the Save button remains disabled until full loading of the page.
Topic on Extension talk:VEForAll/Flow
Appearance
We had the same problem and this solved it for us: https://phabricator.wikimedia.org/T219641