Ubuntu 20.04 多屏不镜像时出错

Question

我在 xubuntu 20.04 上使用双屏时遇到以下问题。我有两个显示器：

VGA-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 480mm x 270mm
   1920x1080     60.00*+
   1680x1050     59.95  
   1400x1050     59.98  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      59.89  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
   720x400       70.08  
DVI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm
   1920x1080     60.00*+
   1680x1050     59.88  
   1280x1024     60.02  
   1280x960      60.00  
   1280x720      60.00  
   1024x768      60.00  
   800x600       60.32  
   640x480       59.94  
   720x400       70.08  
S-video disconnected (normal left inverted right x axis y axis)

和显卡：

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV370 [Radeon X300]

当我选中“镜像”选项时，一切都运行正常。但是当我取消选中它时，一切都开始闪烁，并且两个屏幕上都出现了随机的彩色条纹。

你能帮我这个忙吗？