Application: kwin_x11 (5.21.5)

Qt Version: 5.15.2
Frameworks Version: 5.81.0
Operating System: Linux 5.11.0-36-generic x86_64
Windowing System: X11
Drkonqi Version: 5.21.5
Distribution: Ubuntu 21.04

-- Information about the crash:
- What I was doing when the application crashed:
disable laptop screen in Display Configuration
- Unusual behavior I noticed:
Before disable, I apply Window Rules and UI lags, so I disable laptop screen and re-enable it, then UI lag disappears.
- Custom settings of the application:

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin_x11), signal: Segmentation fault

[KCrash Handler]
#4  0x00007fc1a263e9c9 in KWin::Workspace::constrainedStackingOrder() () at /lib/x86_64-linux-gnu/libkwin.so.5
#5  0x00007fc1a26342e0 in KWin::Workspace::updateStackingOrder(bool) () at /lib/x86_64-linux-gnu/libkwin.so.5
#6  0x00007fc1a27059b1 in KWin::X11Client::setFrameGeometry(QRect const&, KWin::AbstractClient::ForceGeometry_t) () at /lib/x86_64-linux-gnu/libkwin.so.5
#7  0x00007fc1a258f14b in KWin::AbstractClient::qt_metacall(QMetaObject::Call, int, void**) () at /lib/x86_64-linux-gnu/libkwin.so.5
#8  0x00007fc1a25aab6a in KWin::X11Client::qt_metacall(QMetaObject::Call, int, void**) () at /lib/x86_64-linux-gnu/libkwin.so.5
#9  0x00007fc19fa61c01 in QQmlPropertyPrivate::write(QObject*, QQmlPropertyData const&, QVariant const&, QQmlContextData*, QFlags<QQmlPropertyData::WriteFlag>) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#10 0x00007fc19f98c1fb in QV4::QObjectWrapper::setProperty(QV4::ExecutionEngine*, QObject*, QQmlPropertyData*, QV4::Value const&) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#11 0x00007fc19f98cbf7 in QV4::QObjectWrapper::setQmlProperty(QV4::ExecutionEngine*, QQmlContextData*, QObject*, QV4::String*, QV4::QObjectWrapper::RevisionMode, QV4::Value const&) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#12 0x00007fc19f98cd95 in QV4::QObjectWrapper::virtualPut(QV4::Managed*, QV4::PropertyKey, QV4::Value const&, QV4::Value*) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#13 0x00007fc19f91d307 in QV4::Lookup::setterFallback(QV4::Lookup*, QV4::ExecutionEngine*, QV4::Value&, QV4::Value const&) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#14 0x00007fc19f9b4a82 in QV4::Runtime::SetLookupStrict::call(QV4::Function*, QV4::Value const&, int, QV4::Value const&) () at /lib/x86_64-linux-gnu/libQt5Qml.so.5
#15 0x00007fc15d89693d in  ()
#16 0x0000000000000000 in  ()
[Inferior 1 (process 4076) detached]

Reported using DrKonqi