Hello Here's another backtrace that occured when switching on an external screen (plasma is configured to switch off the laptop screen when an exteral LCD is connected. The crash always happens when switching off the external screen (1920x1200 compared to laptop's 1920x1080).
The laptops card is : 01:00.0 VGA compatible controller: NVIDIA Corporation GF106GLM [Quadro 2000M] (rev a1) backtrace: Thread 1 (Thread 0x7f3d968ec940 (LWP 19104)): [KCrash Handler] #6 0x00007f3d81dd74de in QXcbScreen::mapToNative(QRect const&) const () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5 #7 0x00007f3d81ddc713 in QXcbWindow::mapToNative(QRect const&, QXcbScreen const*) const () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5 #8 0x00007f3d81dddf8b in QXcbWindow::propagateSizeHints() () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5 #9 0x00007f3d81de314c in QXcbWindow::setGeometry(QRect const&) () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5 #10 0x00007f3d91c3a3cb in QWindow::resize(QSize const&) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 #11 0x00007f3d91c3a473 in QWindow::resize(int, int) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 #12 0x00007f3cced6f22b in ?? () from /usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/private/notifications/libnotificationshelperplugin.so #13 0x00007f3cced7018a in ?? () from /usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/private/notifications/libnotificationshelperplugin.so #14 0x00007f3d91920f8a in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 #15 0x00007f3d93f046f1 in QQmlVMEMetaObject::metaCall(QMetaObject::Call, int, void**) () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #16 0x00007f3d93f5d119 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #17 0x00007f3d93ee29ce in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #18 0x00007f3d93ee3915 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #19 0x00007f3d93ee41dd in QV4::QObjectMethod::callInternal(QV4::CallData*) () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #20 0x00007f3d93efada3 in QV4::Runtime::callProperty(QV4::ExecutionEngine*, int, QV4::CallData*) () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #21 0x00007f3cced59af0 in ?? () #22 0x00007f3d64487644 in ?? () #23 0x00007f3d93f99bc9 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 #24 0x0000000000000000 in ?? () HTH