External monitor(s) dark out on one account and I cannot set monitor layout, how to fix?

Question

Seemingly "out of nowhere", my Dell e7440 running Ubuntu 16.04 with 2 external monitors displays only the login screen for external monitors, when I login it shows system error and external monitors will dark out.

Couldn't see the display options as well:

could not get screen information

PS: Everything works in guest session

What could be wrong with my setup?

---

This didn't help:

sudo apt-get install --reinstall ubuntu-desktop

(From this post)

Output of xrandr, as requested in a comment:

Screen 0: minimum 8 x 8, current 6400 x 1440, maximum 32767 x 32767
eDP1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1920x1080     60.02*+  59.93  
   1680x1050     59.95    59.88  
   1600x1024     60.17  
   1400x1050     59.98  
   1600x900      60.00  
   1280x1024     60.02  
   1440x900      59.89  
   1280x960      60.00  
   1368x768      60.00  
   1360x768      59.80    59.96  
   1152x864      60.00  
   1280x720      60.00  
   1024x768      60.00  
   1024x576      60.00  
   960x540       60.00  
   800x600       60.32    56.25  
   864x486       60.00  
   640x480       59.94  
   720x405       60.00  
   640x360       60.00  
DP1 disconnected (normal left inverted right x axis y axis)
DP1-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 527mm x 296mm
   1920x1080     60.00*+  50.00    59.94  
   1600x1200     60.00  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.08    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
DP1-2 connected 2560x1440+3840+0 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440     59.95*+
   2048x1152     60.00  
   1920x1200     59.88  
   1920x1080     60.00    50.00    59.94    30.00    25.00    24.00    29.97    23.98  
   1600x1200     60.00  
   1680x1050     59.95  
   1280x1024     75.02    60.02  
   1200x960      59.99  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.08    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
DP1-3 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Answer 1

Corrupted monitors.xml file

As mentioned in a comment, if your monitors darken on (only) one account, working on other(s), most likely your monitors.xml file is somehow corrupted. To fix, remove ~/.config/monitors.xml, immediately log out and back in.

Setting up your (complicated) monitor setup from cli

You mentioned the step above fixed the darkening screen(s), but you still cannot setup the screens in the layout you wanted (see below). That is possibly caused by a bug. We might very well be able to work around it by setting it up from cli.

To set up the screen layout as you described in a comment:

You'd need to run the xrandr command:

xrandr --output DP1-1 --pos 0x0 \
--output DP1-2 --pos 1920x0 \
--output DP1-1 --pos 0x360 \
--output eDP1 --pos 1440x1440

...if I made no typo or other mistake...

Explanation

Normally, in a complicated screen layout, you simply need to work from left to right, from top to bottom.

However
If you don't know for sure what is the current layout, you cannot place the first screen, other than 0x0. If there is empty space in the top of your screen layout, xrandr will remove the empty space and change e.g. 0x200 into 0x0. Therefore the steps need to be:

1. position DP1-1 and DP1-2 horizontally top-alligned:

   xrandr --output DP1-1 --pos 0x0 --output DP1-2 --pos 1920x0
   

   

2. only then bottom-align DP1-1 with DP1-2:

   xrandr --output DP1-1 --pos 0x360
   

   

3. place eDP1 in the middle below the other two screens:

   xrandr --output eDP1 --pos 1440x1280
   

   

How to use

1. Copy the small script below into an empty file, save it as setup_screens.sh

   #!/bin/bash
   
   xrandr --output DP1-1 --pos 0x0 \
   --output DP1-2 --pos 1920x0 \
   --output DP1-1 --pos 0x360 \
   --output eDP1 --pos 1440x1440
   

2. Make it executable

3. Test-run it from a terminal, run the command:

   /path/to/setup_screens.sh
   

4. Either run it from a shortcut key: choose: System Settings > "Keyboard" > "Shortcuts" > "Custom Shortcuts". Click the "+" and add the command:

   /path/to/setup_screens.sh
   

   or run it on login: Dash > Startup Applications > Add. Add the command:

   /bin/bash -c "sleep 15 && /path/to/setup_screens.sh"