orca --setup hangs in second KDE session

$ lsb_release -rd
Description: Ubuntu 19.10
Release: 19.10

$ apt-cache policy orca
orca:
  Installed: 3.34.0-1ubuntu3
  Candidate: 3.34.0-1ubuntu3
  Version table:
 *** 3.34.0-1ubuntu3 500
        500 http://be.archive.ubuntu.com/ubuntu eoan/main amd64 Packages
        500 http://be.archive.ubuntu.com/ubuntu eoan/main i386 Packages
        100 /var/lib/dpkg/status

I run KDE. I boot my system and log in with user A. "orca --setup" works normally with user A. Then I go to the KDE Application launcher menu, and select "Leave", then "Switch User". Then I click "Start a new session", and log in as user B. Next, I run "orca --setup". I expect the Orca Screen Reader Preferences window to appear with the preferences. Instead, the KDE window frame appears, but remains empty and does not respond. In the console, I see:

$ orca --setup

(orca:6122): dbind-WARNING **: 10:25:27.540: Couldn't get application list: Message recipient disconnected from message bus without replying
/usr/lib/python3/dist-packages/pyatspi/registry.py:206: Warning: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
  return Atspi.get_desktop(i)

** (orca:6122): WARNING **: 10:25:28.245: AT-SPI: Could not obtain desktop path or name

** (orca:6122): WARNING **: 10:25:28.250: atk-bridge: get_device_events_reply: unknown signature

** (orca:6122): WARNING **: 10:25:28.250: atk-bridge: get_device_events_reply: unknown signature

** (orca:6122): WARNING **: 10:25:28.250: atk-bridge: GetRegisteredEvents returned message with unknown signature

** (orca:6122): WARNING **: 10:25:28.250: AT-SPI: Could not obtain desktop path or name

** (orca:6122): WARNING **: 10:25:28.255: AT-SPI: Could not obtain desktop path or name

...

(orca:6122): dbind-WARNING **: 10:25:28.402: RegisterKeystrokeListener failed: Message recipient disconnected from message bus without replying

** (orca:6122): WARNING **: 10:25:28.409: AT-SPI: Could not obtain desktop path or name

(orca:6122): dbind-WARNING **: 10:25:28.402: RegisterKeystrokeListener failed: Message recipient disconnected from message bus without replying

** (orca:6122): WARNING **: 10:25:28.409: AT-SPI: Could not obtain desktop path or name

...