I'm having similar. When machine dims the display, it's changing my monitors brightness and doesn't bounce back.
I just realized I was on X11 when I checked logs. I'm going to try it on Wayland (which is what I normally use) and see if it continues.
What I did notice is that changing my Dim settings to 1 minute and letting it take effect to test did not seem to make it happen. It seems like it takes longer, like overnight.
I am on Wayland and have the issue.
I realized it happened with me whenever my computer was idle for a few minutes and the monitor turned off. Eventually it fixed itself, but it sure was annoying having to change the brightness back to the value it was before it went on stand-by.
Here are the settings I used to stop this from happening.
I have this issue too.
I disabled the dimming because often it would not return it back to 100% for some reason. Dunno. One of those KDE things.
What confuses me is that the dimming is set to 70%, not the 20% it comes back at. And only if I leave it overnight or something, not if I just set the timer to 1 minute and test it.
I think mine went to 70% or something, even though I had it set to 100%. I don't know for sure though, because the weird thing was that the slider in the tray icon was still at 100%. So I had to "reduce" the brightness and then max it out again to reach proper 100%.
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