Cinnamon: Restore VirtualBox full screen window on same monitor when unlocking

I run Cinnamon. That locks the screen after some time. If I unlock, the VirtualBox full screen moves to the main monitor (and is there full screen).

Is it possible that Cinnamon keeps the windows on the monitor it was before the lock?

It seems that also other applications are moved around.

Moreover, when starting Firefox, its opening windows are not re-assigned workspaces, but are moved to the current workspace.