Of course, the day after I post this report, an update appears to have fixed the bug. I can't really tell which package was responsible. Here's the list
Install: libwayland-egl1:amd64 (1.16.0-1ubuntu1~oibaf~b,) gnome-software:amd64 (3.28.1-0ubuntu4.18.04.4, 3.28.1-0ubuntu4.18.04.5,) gnome-software-common:amd64 (3.28.1-0ubuntu4.18.04.4, 3.28.1-0ubuntu4.18.04.5,) gnome-software-plugin-snap:amd64 (3.28.1-0ubuntu4.18.04.4, 3.28.1-0ubuntu4.18.04.5,) kmod:amd64 (24-1ubuntu3, 24-1ubuntu3.1,) libdrm2:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm2:i386 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-amdgpu1:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-amdgpu1:i386 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-common:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b) libdrm-intel1:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-intel1:i386 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-nouveau2:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-nouveau2:i386 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-radeon1:amd64 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libdrm-radeon1:i386 (2.4.96+git1810220630.9d07fb~oibaf~b, 2.4.96+git1811020630.b3dec0~oibaf~b,) libegl1-mesa:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) libegl-mesa0:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) libgbm1:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) libgl1-mesa-glx:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) libkmod2:amd64 (24-1ubuntu3, 24-1ubuntu3.1,) libpython3-stdlib:amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,) libwayland-egl1-mesa:amd64 (18.0.5-0ubuntu0~18.04.1, 18.3~git1811011930.1f4110~oibaf~b,) libxatracker2:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) linux-generic:amd64 (4.15.0.37.39, 4.15.0.39.41,) linux-headers-4.15.0-39:amd64 (4.15.0-39.42, automatic,) linux-headers-4.15.0-39-generic:amd64 (4.15.0-39.42, automatic,) linux-image-4.15.0-39-generic:amd64 (4.15.0-39.42, automatic) linux-image-generic:amd64 (4.15.0.37.39, 4.15.0.39.41,) linux-modules-4.15.0-39-generic:amd64 (4.15.0-39.42, automatic,) linux-modules-extra-4.15.0-39-generic:amd64 (4.15.0-39.42, automatic,) mesa-va-drivers:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) mesa-vdpau-drivers:amd64 (18.3~git1810241930.edc06d~oibaf~b, 18.3~git1811011930.1f4110~oibaf~b,) python3:amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,) python3-gdbm:amd64 (3.6.5-3, 3.6.7-1~18.04,) python3-minimal:amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,) xkb-data:amd64 (2.23.1-1ubuntu1, 2.23.1-1ubuntu1.18.04.1,) xserver-xorg-video-amdgpu:amd64 (18.1.99+git1810241933.c9d43c~oibaf~b, 18.1.99+git1810291933.1cb338~oibaf~b,) Upgrade: libcurl3-gnutls:amd64 (7.58.0-2ubuntu3.3, 7.58.0-2ubuntu3.5) Upgrade: libcurl4:amd64 (7.58.0-2ubuntu3.3, 7.58.0-2ubuntu3.5) Upgrade: linux-headers-generic:amd64 (4.15.0.37.39, 4.15.0.39.41,)
SOLVED for me.
Of course, the day after I post this report, an update appears to have fixed the bug. I can't really tell which package was responsible. Here's the list
Install: libwayland- egl1:amd64 (1.16.0- 1ubuntu1~ oibaf~b, ) software: amd64 (3.28.1- 0ubuntu4. 18.04.4, 3.28.1- 0ubuntu4. 18.04.5, ) software- common: amd64 (3.28.1- 0ubuntu4. 18.04.4, 3.28.1- 0ubuntu4. 18.04.5, ) software- plugin- snap:amd64 (3.28.1- 0ubuntu4. 18.04.4, 3.28.1- 0ubuntu4. 18.04.5, ) git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) amdgpu1: amd64 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) amdgpu1: i386 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) common: amd64 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b) intel1: amd64 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) nouveau2: amd64 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) nouveau2: i386 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) radeon1: amd64 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) radeon1: i386 (2.4.96+ git1810220630. 9d07fb~ oibaf~b, 2.4.96+ git1811020630. b3dec0~ oibaf~b, ) 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) mesa-glx: amd64 (18.3~git181024 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) stdlib: amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,) egl1-mesa: amd64 (18.0.5- 0ubuntu0~ 18.04.1, 18.3~git1811011 930.1f4110~ oibaf~b, ) amd64 (18.3~git181024 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) generic: amd64 (4.15.0.37.39, 4.15.0.39.41,) headers- 4.15.0- 39:amd64 (4.15.0-39.42, automatic,) headers- 4.15.0- 39-generic: amd64 (4.15.0-39.42, automatic,) image-4. 15.0-39- generic: amd64 (4.15.0-39.42, automatic) image-generic: amd64 (4.15.0.37.39, 4.15.0.39.41,) modules- 4.15.0- 39-generic: amd64 (4.15.0-39.42, automatic,) modules- extra-4. 15.0-39- generic: amd64 (4.15.0-39.42, automatic,) drivers: amd64 (18.3~git181024 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) drivers: amd64 (18.3~git181024 1930.edc06d~ oibaf~b, 18.3~git1811011 930.1f4110~ oibaf~b, ) minimal: amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,) 1ubuntu1. 18.04.1, ) xorg-video- amdgpu: amd64 (18.1.99+ git1810241933. c9d43c~ oibaf~b, 18.1.99+ git1810291933. 1cb338~ oibaf~b, ) gnutls: amd64 (7.58.0-2ubuntu3.3, 7.58.0-2ubuntu3.5) generic: amd64 (4.15.0.37.39, 4.15.0.39.41,)
gnome-
gnome-
gnome-
kmod:amd64 (24-1ubuntu3, 24-1ubuntu3.1,)
libdrm2:amd64 (2.4.96+
libdrm2:i386 (2.4.96+
libdrm-
libdrm-
libdrm-
libdrm-
libdrm-intel1:i386 (2.4.96+
libdrm-
libdrm-
libdrm-
libdrm-
libegl1-mesa:amd64 (18.3~git181024
libegl-mesa0:amd64 (18.3~git181024
libgbm1:amd64 (18.3~git181024
libgl1-
libkmod2:amd64 (24-1ubuntu3, 24-1ubuntu3.1,)
libpython3-
libwayland-
libxatracker2:
linux-
linux-
linux-
linux-
linux-
linux-
linux-
mesa-va-
mesa-vdpau-
python3:amd64 (3.6.5-3ubuntu1, 3.6.7-1~18.04,)
python3-gdbm:amd64 (3.6.5-3, 3.6.7-1~18.04,)
python3-
xkb-data:amd64 (2.23.1-1ubuntu1, 2.23.1-
xserver-
Upgrade: libcurl3-
Upgrade: libcurl4:amd64 (7.58.0-2ubuntu3.3, 7.58.0-2ubuntu3.5)
Upgrade: linux-headers-
SOLVED for me.