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 Desktop Packages, which is subscribed to gnome-control-center in Ubuntu. https://bugs.launchpad.net/bugs/1757068 Title: Night light brakes when screen dims Status in gnome-control-center package in Ubuntu: Confirmed Bug description: I'm using the night light function in Budgie which is set to a temperature of 4000 and the schedule is set from sunset to sunrise. When my display dims after X minutes of inactivity the night light function breaks which results in a much blue-er screen. When I move my mouse the dimming effect dissapears but and the temperature and brightness of my screen go back to the default value as if the night light function isn't on. Disabling and enabling the night light function fixes the issue until my screen dims again. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1757068/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
