There was a message in backlight sevice:
> systemctl status systemd-backlight@backlight\:intel_backlight.service
intel_backlight: Saved brightness 192 is too low; increasing to 960.
Fixed with: sudo nano /usr/lib/udev/rules.d/99-systemd.rules and adding ENV{ID_BACKLIGHT_CLAMP}+="false", to the line SUBSYSTEM=="backlight"
That is: SUBSYSTEM=="backlight", TAG+="systemd", IMPORT{builtin}="path_id", ENV{ID_BACKLIGHT_CLAMP}+="false", ENV{SYSTEMD_WANTS}+="systemd-backlight@backlight:$name.service"