Tested in Talk:Sandbox.

When there's an embedded image with position (left, rigth, center, none), when using Visual Editor, the image disappears, and "null" appears instead. Switching to code changes it to a "null" image wrapping the original one.

This is the wiki code of the description:

[[File:Kitten (06) by Ron.jpg|left|150px]]

When switching to VE and then to code, the code looks as this:

[[null|left|0x0px|link=|alt=null|[[File:Kitten (06) by Ron.jpg|link=|150x150px]]]]

I've tested the same code on Visual Editor on a normal page and this problem doesn't happen. I don't know if it has to do with Flow or VisualEditor