Whether this happens or not depends either on the relative position of the two screens (moving LVDS so that its bottom is lower than the bottom of VGA seems to trigger this), and on whether I disable the screens with the gnome-display-settings (no bug), or with 'xrandr --output VGA --auto --output LVDS --off' (triggers bug).
The exact sequence of commands I can use to reproduce this is
Whether this happens or not depends either on the relative position of the two screens (moving LVDS so that its bottom is lower than the bottom of VGA seems to trigger this), and on whether I disable the screens with the gnome-display- settings (no bug), or with 'xrandr --output VGA --auto --output LVDS --off' (triggers bug).
The exact sequence of commands I can use to reproduce this is
1. xrandr --output VGA --auto --rotate left --right-of LVDS
2. xrandr --output LVDS --auto --pos 0x480
3. xrandr --output LVDS --auto --output VGA --off