Field Settings lost after moving on layout

Field settings get lost when fields are moved on the layout.

Reprocuer:
1.- Open a form
2.- Add fields & move them on layout.
3.- Save form and open again
4.- Error appears on screen when rendering the fields that have been moved.

The cause seems to be that when fields are moved they are fisically removed from the layout (and the form) but never added back when droped on the final region.