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Resetting Display brightness/gamma on external Display doesn’t work

I managed to mess up the output on my external Display. I don’t know how, exactly. I am running Pop OS and recently upgraded to 19.10. Shortly after I noticed the problem that the display settings on my my external monitor are messed up. There seems to be a gamma/brightness misadjustment. The screen is not (only) too bright but lacks contrast.
I had the same problem a while ago when the brightness settings of a game (Urban Terror) messed up the brightness of the screen, even after the game was closed. So maybe it’s this problem again. I used to solve it by running the game, changing the brightness to default and exit. Now that doesn’t work anymore.
What I tried:
– Adjusting the brightness and gamma values through xrandr. I tried setting everything to “1”, as well as trying different values. I could change the output, but not get rid of the problem entirely, there is still a very visible lack of contrast. It’s like there is a layer of fog in front of the screen.

-Since the display used to work ok out of the box I thought I could just remove the display mode through xrandr, hoping I could set everything as it was originally when reconnected.
It didn’t work though, here is the output:

X@pop-os:~$ xrandr --delmode DP-2-2 1920x1080
X Error of failed request:  BadAccess (attempt to access private resource denied)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  19 (RRDeleteOutputMode)
  Serial number of failed request:  40
  Current serial number in output stream:  41

In a pretty similar question this bug was referred, but not resolved:
https://bugs.launchpad.net/ubuntu/+source/x11-xserver-utils/+bug/364091

  • I also tried removing the monitors.xml file, didn’t work either.

Is there a way to just set everything back to zero? I don’t need any of the settings that I used, so if everything would be at the default settings again I would be happy.. I am sorry if I should have posted the question in one of the existing similar threads, or split this question into several more specific ones.

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