Probably a bug in Plasma 5.17 backports for ubuntu 19.10. Oracle Virtualbox and VLC crashed. See all log and talk here: https://forums.virtualbox.org/viewtopic.php?f=7&t=95428
The backtrace only shows Qt code, no KDE code. Please install debug symbols for Qt libraries and report this issue directly to Qt developers via https://bugreports.qt.io/ Backtrace from forum link: Thread 1 (Thread 0x7f005675b9c0 (LWP 7992)): #0 0x00007f005b01dee8 in QWindow::isTopLevel() const () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #1 0x00007f005b020c28 in QWindowPrivate::maybeQuitOnLastWindowClosed() () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #2 0x00007f005b024bf1 in QWindow::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #3 0x00007f005aa2626c in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5 No symbol table info available. #4 0x00007f005a9c4a86 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5 No symbol table info available. #5 0x00007f005a9cde00 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5 No symbol table info available. #6 0x00007f005b75ea9a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 No symbol table info available. #7 0x00007f005b016cb5 in QGuiApplicationPrivate::processCloseEvent(QWindowSystemInterfacePrivate::CloseEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #8 0x00007f005b01b622 in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #9 0x00007f005aff526b in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 No symbol table info available. #10 0x00007f005562c28e in ?? () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5 No symbol table info available. #11 0x00007f00592f284d in g_main_context_dispatch () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 No symbol table info available. #12 0x00007f00592f2ad0 in ?? () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 No symbol table info available. #13 0x00007f00592f2b73 in g_main_context_iteration () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 No symbol table info available. #14 0x00007f005b7b66a5 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 No symbol table info available. #15 0x00007f005b75d63b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 No symbol table info available. #16 0x00007f005b7653a6 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5