Ubuntu 16.04 菜单显示不正确且桌面背景变黑

Question

我的 ubuntu 16.04 上的菜单图标显示不正确。

例如下面的声音菜单中缺少滑动条。

此外，我的 Ubuntu 背景一直变黑。

输出xrandr

Screen 0: minimum 320 x 200, current 3840 x 1200, maximum 8192 x 8192
VGA-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
HDMI-2 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00  
   1600x1200     60.00  
   1680x1050     59.88  
   1280x1024     60.02  
   1280x960      60.00  
   1024x768      60.00  
   800x600       60.32  
   640x480       59.94  
   720x400       70.08  
DP-1 connected primary 1920x1200+1920+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00  
   1600x1200     60.00  
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     60.02  
   1440x900      59.89  
   1280x800      59.81  
   1280x720      60.00  
   1024x768      60.00  
   800x600       60.32  
   640x480       59.94  
HDMI-3 disconnected (normal left inverted right x axis y axis)