Ubuntu desktop 20.04 LTS screen doesn't wake after going to sleep

I’m having an issue with Ubuntu desktop 20.04 where my screen won’t switch on after going to sleep. When I press a key to wake the system up after the screensaver it doesn’t come back for some reason. The problem seems intermittent, when I press the power button on the screen it doesn’t show the OSD message (so there is a signal) but the screen is completely blank. If I leave it for a few minutes, the signal will disappear and then the OSD message comes back. If I power the screen on first and then press a key on the keyboard, the login page will show about 50% of the time. Sometimes pressing the power key will help. When the display is malfunctioning I cannot bring up the terminal with CTRL + ALT + F3.

I’m using an external monitor connected by HDMI, and an Nvidia graphics card (the drivers all seem to be set up correctly). I actually noticed this problem with onboard graphics (before installing the nvidia card) so I don’t think it’s driver related.
I noticed that there are some apparmor denials the dmesg log on /org/freedesktop/ paths around the same time (are these related)? I don’t know very much about apparmor so would appreciate some guidance there. I’m not using any custom apparmor profiles.

Thanks ūüôā

Code:

# dmesg log
[  288.854836] audit: type=1400 audit(1609595950.565:89): apparmor="DENIED" operation="capable" profile="/snap/snapd/10492/usr/lib/snapd/snap-confine" pid=2836 comm="snap-confine" capability=4  capname="fsetid"
[  290.107404] audit: type=1326 audit(1609595951.817:90): auid=1000 uid=1000 gid=1000 ses=4 pid=2836 comm="snap-store" exe="/snap/snap-store/518/usr/bin/snap-store" sig=0 arch=c000003e syscall=314 compat=0 ip=0x7f4bff739639 code=0x50000
[  290.370340] audit: type=1107 audit(1609595952.077:91): pid=759 uid=103 auid=4294967295 ses=4294967295 msg='apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/org/freedesktop/NetworkManager" interface="org.freedesktop.DBus.Properties" member="GetAll" mask="send" name=":1.13" pid=2836 label="snap.snap-store.ubuntu-software" peer_pid=761 peer_label="unconfined"
                exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[  290.887571] audit: type=1107 audit(1609595952.597:92): pid=759 uid=103 auid=4294967295 ses=4294967295 msg='apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/org/freedesktop/PolicyKit1/Authority" interface="org.freedesktop.DBus.Properties" member="GetAll" mask="send" name=":1.11" pid=2836 label="snap.snap-store.ubuntu-software" peer_pid=782 peer_label="unconfined"
                exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[  290.887979] audit: type=1107 audit(1609595952.597:93): pid=759 uid=103 auid=4294967295 ses=4294967295 msg='apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/org/freedesktop/PolicyKit1/Authority" interface="org.freedesktop.PolicyKit1.Authority" member="CheckAuthorization" mask="send" name=":1.11" pid=2836 label="snap.snap-store.ubuntu-software" peer_pid=782 peer_label="unconfined"
                exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[  290.909562] audit: type=1107 audit(1609595952.617:94): pid=759 uid=103 auid=4294967295 ses=4294967295 msg='apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/org/freedesktop/PolicyKit1/Authority" interface="org.freedesktop.DBus.Properties" member="GetAll" mask="send" name=":1.11" pid=2836 label="snap.snap-store.ubuntu-software" peer_pid=782 peer_label="unconfined"
                exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[  290.909914] audit: type=1107 audit(1609595952.617:95): pid=759 uid=103 auid=4294967295 ses=4294967295 msg='apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/org/freedesktop/PolicyKit1/Authority" interface="org.freedesktop.PolicyKit1.Authority" member="CheckAuthorization" mask="send" name=":1.11" pid=2836 label="snap.snap-store.ubuntu-software" peer_pid=782 peer_label="unconfined"
                exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[  291.197614] audit: type=1400 audit(1609595952.905:96): apparmor="DENIED" operation="open" profile="snap.snap-store.ubuntu-software" name="/etc/PackageKit/Vendor.conf" pid=2836 comm="snap-store" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[  298.196733] audit: type=1400 audit(1609595959.905:97): apparmor="DENIED" operation="open" profile="snap.snap-store.ubuntu-software" name="/var/lib/snapd/hostfs/usr/share/gdm/greeter/applications/gnome-initial-setup.desktop" pid=2836 comm="pool-org.gnome." requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[  298.219801] audit: type=1400 audit(1609595959.929:98): apparmor="DENIED" operation="open" profile="snap.snap-store.ubuntu-software" name="/var/lib/snapd/hostfs/usr/share/gdm/greeter/applications/gnome-initial-setup.desktop" pid=2836 comm="pool-org.gnome." requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

# Graphics driver info
$ nvidia-smi
Sat Jan  2 14:33:26 2021     
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 460.27.04    Driver Version: 460.27.04    CUDA Version: 11.2    |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|        Memory-Usage | GPU-Util  Compute M. |
|                              |                      |              MIG M. |
|===============================+======================+======================|
|  0  GeForce GTX 105...  On  | 00000000:10:00.0  On |                  N/A |
| 35%  32C    P5    N/A /  75W |    480MiB /  4006MiB |      0%      Default |
|                              |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
                                                                             
+-----------------------------------------------------------------------------+
| Processes:                                                                  |
|  GPU  GI  CI        PID  Type  Process name                  GPU Memory |
|        ID  ID                                                  Usage      |
|=============================================================================|
|    0  N/A  N/A      1099      G  /usr/lib/xorg/Xorg                101MiB |
|    0  N/A  N/A      2429      G  /usr/lib/xorg/Xorg                254MiB |
|    0  N/A  N/A      2564      G  /usr/bin/gnome-shell              108MiB |
|    0  N/A  N/A      3854      G  /usr/lib/firefox/firefox            1MiB |
|    0  N/A  N/A      5364      G  /usr/lib/firefox/firefox            1MiB |
+-----------------------------------------------------------------------------+


 

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