Failing to power save the screen

For some time now (several kernel updates) power save of the screen on my desktop computer has been failing. The screensaver is left running / visible.

I loaded the system with Xubuntu 20.04.2 DVD image... it was the first release of 20.04.x that would boot on my new system.

It is based on a MSI MPG Z490 motherboard. It has an EVGA GeForce GT 1030 SC 2GB GDDR5 Low Profile Graphics Card 02G-P4-6332-KR video card in it. I run the NVIDIA Binary drivers, "Additional Drivers" shows I am using the nvidia-driver-470 package.

I use the Skyrocket screen saver that comes in the rss-glx package.

When it started acting up, then the screen saver would be left running visibly, the screen would not go to sleep / power save. An IPL (reboot) of the system would fix it and again power save would be entered successfully after the 20 minutes. Now even with a fresh IPL, first time the screen saver comes on, the system refuses to power save the screen. It will run all night in screensaver mode.

My system is now running kernel:
$ uname -a
Linux jaakob 5.15.0-41-generic #44~20.04.1-Ubuntu SMP Fri Jun 24 13:27:29 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

$ dpkg -l | grep linux-
ii binutils-x86-64-linux-gnu 2.34-6ubuntu1.3 amd64 GNU binary utilities, for x86-64-linux-gnu target
ii linux-base 4.5ubuntu3.7 all Linux image base package
ii linux-firmware 1.187.32 all Firmware for Linux kernel drivers
ii linux-generic-hwe-20.04 5.15.0.41.44~20.04.13 amd64 Complete Generic Linux kernel and headers
ii linux-headers-5.15.0-41-generic 5.15.0-41.44~20.04.1 amd64 Linux kernel headers for version 5.15.0 on 64 bit x86 SMP
ii linux-headers-generic-hwe-20.04 5.15.0.41.44~20.04.13 amd64 Generic Linux kernel headers
ii linux-hwe-5.15-headers-5.15.0-41 5.15.0-41.44~20.04.1 all Header files related to Linux kernel version 5.15.0
ii linux-image-5.15.0-41-generic 5.15.0-41.44~20.04.1 amd64 Signed kernel image generic
ii linux-image-generic-hwe-20.04 5.15.0.41.44~20.04.13 amd64 Generic Linux kernel image
ii linux-libc-dev:amd64 5.4.0-122.138 amd64 Linux Kernel Headers for development
ii linux-modules-5.15.0-41-generic 5.15.0-41.44~20.04.1 amd64 Linux kernel extra modules for version 5.15.0 on 64 bit x86 SMP
ii linux-modules-extra-5.15.0-41-generic 5.15.0-41.44~20.04.1 amd64 Linux kernel extra modules for version 5.15.0 on 64 bit x86 SMP
ii linux-sound-base 1.0.25+dfsg-0ubuntu5 all base package for ALSA and OSS sound systems

Please advise what other diagnostics I may provide to investigate why the power management is failing to put my display into sleep mode after the configured time.
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ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.24
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2021-06-27 (384 days ago)
InstallationMedia: Xubuntu 20.04.2 LTS "Focal Fossa" - Release amd64 (20210204)
NonfreeKernelModules: nvidia_modeset nvidia
Package: xfce4-power-manager 1.6.6-1
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 5.15.0-41.44~20.04.1-generic 5.15.39
Tags: focal
Uname: Linux 5.15.0-41-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True