Bug#866772: Debian 10 - dual displays - bug still present

[Torfinn Ingolfsen <tingox@gmail.com>]

I've been running Debian 9 for a long time with this dual display
setup and never had any problems. Upgraded to Debian 10 about a week
ago, and immediately have this problem.
xrandr info:
tingo@kg-bsbox:~$ xrandr
Screen 0: minimum 320 x 200, current 2400 x 1920, maximum 8192 x 8192
HDMI-1 connected primary 1200x1920+0+0 left (normal left inverted
right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    60.00    50.00    59.94    24.00    23.98
   1920x1080i    60.00    60.00    50.00    59.94
   1600x1200     60.00
   1280x1024     75.02    60.02
   1152x864      75.00
   1280x720      60.00    60.00    50.00    59.94
   1024x768      75.03    60.00
   800x600       75.00    60.32
   720x576       50.00    50.00
   720x576i      50.00    50.00
   720x480       60.00    60.00    59.94    59.94    59.94
   720x480i      60.00    60.00    59.94    59.94
   640x480       75.00    60.00    59.94    59.94
   720x400       70.08
DP-1 connected 1200x1920+1200+0 left (normal left inverted right x
axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    60.00    50.00    59.94    24.00    23.98
   1920x1080i    60.00    60.00    50.00    59.94
   1600x1200     60.00
   1280x1024     75.02    60.02
   1152x864      75.00
   1280x720      60.00    60.00    50.00    59.94
   1024x768      75.03    60.00
   800x600       75.00    60.32
   720x576       50.00    50.00
   720x480       60.00    60.00    59.94    59.94    59.94
   640x480       75.00    60.00    59.94    59.94
   720x400       70.08

The machine is an ASRock BeeBox-S 7100U.

Details / workaround:
pressing Ctrl-Alt-F7 gets me to the "this session is locked" screen
and in a few seconds I get to the unlock screen and can give my
password.
(but it is annoying to have to do this many times a day).
Also, the second / right display often has changed rotation back to
"normal" when the bug hits, and I have to go into Settings, Display
and change it back.
My estimate is that about half the times I need to unlock I see the
bug, the other half it works as it should

reportbug output
-- System Information:
Debian Release: 10.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8),
LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages xfce4 depends on:
ii  gtk2-engines-xfce        3.2.0-4
ii  libxfce4ui-utils         4.12.1-3
ii  thunar                   1.8.4-1
ii  xfce4-appfinder          4.12.0-2
ii  xfce4-panel              4.12.2-1
ii  xfce4-pulseaudio-plugin  0.4.1-1
ii  xfce4-session            4.12.1-6
ii  xfce4-settings           4.12.4-1
ii  xfconf                   4.12.1-1
ii  xfdesktop4               4.12.4-2
ii  xfwm4                    4.12.5-1

Versions of packages xfce4 recommends:
ii  desktop-base      10.0.2
ii  tango-icon-theme  0.8.90-7
ii  thunar-volman     0.9.1-1
ii  xfce4-notifyd     0.4.3-1
ii  xorg              1:7.7+19

Versions of packages xfce4 suggests:
pn  gtk3-engines-xfce    <none>
ii  xfce4-goodies        4.12.6
ii  xfce4-power-manager  1.6.1-1

-- no debconf information

-- 
Regards,
Torfinn Ingolfsen