I believe I have the same issue. I originally reported it as the current duplicate Bug #1791659.
The issue is as described here: the night light mode turns off as the screen starts dimming right before it blanks. The mode then needs to be turned off and on to work again. If I have an external monitor connected, as "join monitors", the external monitor is the one that loses the night light, whereas the built-in display still has it. The workaround around this is unplugging and plugging the screen back in. I use the following: gnome-control-center version: 1:3.28.2-0ubuntu0.18.04.2 gnome-shell version: 3.28.3-0ubuntu0.18.04.2 System details: OS: Ubuntu 18.04.1 LTS x86_64 Host: N230WU Kernel: 4.15.0-33-lowlatency Uptime: 3 days, 1 hour, 12 mins Packages: 2921 Shell: bash 4.4.19 Resolution: 1920x1080, 1920x1080 DE: Budgie WM: Mutter(Budgie) Theme: Adwaita [GTK2/3] Icons: Adwaita [GTK2/3] Terminal: tilix CPU: Intel i7-8550U (8) @ 4.000GHz GPU: Intel UHD Graphics 620 Memory: 4168MiB / 15918MiB -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1757068 Title: Night light brakes when screen dims To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1757068/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
