Same problem here.
I created a new user role, called video.
A configured that the users belonging to the role video, could see only one sidebar, and only one widget.
When a user with role video changed something in the sidebar, where he was allowed, this happened:
– in the sidebar where he was allowed, all warked well, his modifications affected only the widget which he was allowed to manage.
– all the other sidebars lost all widgets.
I would be happy to see a solution to this bug.
Please anyone knowing a fix let me know!