Backlight control dosn't work on login screen, brightness reset after reboot

Hello, dear friends!

I have minor but annoying issues with laptop screen brightness. I started using my laptop as development/ML rig. Brightness control doesn't work on Gnome login screen, but starts working after logging into my user account. After that it also works on desktop lock screen.

Additional information: I suspect that driver probing is done twice. First - on system boot, second - on user login. I see specific screen blinking.

In journal I see bunch of repeating messages (brightness value isn't always 44):

pkexec[3148]: gdm: The value for the SHELL variable was not found the /etc/shells file [USER=root] [TTY=unknown] [CWD=/var/lib/gdm] [COMMAND=/usr/libexec/gsd-backlight-helper /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/nvidia_0 44]
gsd-power[2671]: Error executing backlight helper: Child process stopped by signal 0
org.gnome.SettingsDaemon.Power.desktop[2671]: This incident has been reported.
org.gnome.SettingsDaemon.Power.desktop[2671]: The value for the SHELL variable was not found the /etc/shells file

It looks like following messages are generated when I use backlight control from login screen, because after login I see similar but successful (at least controls were working).

xxx: Executing command [USER=root] [TTY=unknown] [CWD=/home/xxx] [COMMAND=/usr/libexec/gsd-backlight-helper /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/baclight/nvidia_0 29]
pkexec[4969]: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
pkexec[4969]: pam_systemd(polkit-1:session): Cannot create session: Already running in a session or user slice

Another issue: brightness level is reset after system reboot setting maximum birghtness. In logs I see following (but before driver probing):

 /usr/libexec/gdm-x-session[2283]: (--) NVIDIA(0): Valid display device(s) on GPU-0 at PCI:1:0:0
systemd[1]: Started Load/Save Screen Backlight Brightness of backlight:nvidia_0.
systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:nvidia_0...
systemd[2239]: Startup finished in 885ms.

My rig: Asus G751JT with nVidia GTX970m 3Gb
RHEL 8.1,
nvidia-driver-440.33.01-1.el8.x86_64
nvidia-driver-cuda-440.33.01-1.el8.x86_64
gdm-3.28.3-22.el8.x86_64

To sum up with issues:
1. Brightness isn't restored (but system attempeted to do this) on boot
2. Brightness control starts working only after login
3. Double probing of nVidia driver

Any help with fixing this is appreciated.

PS: all journal lines are in reversed order (from journalctl -r)