Happens on 4.1.4997-dev (3e7dbdea). I updated macOS to 14.4.1 (23E224) today, which I hope is not relevant.
Weird enough, this only reproduces on a release build from the build server. It does not reproduce locally, despite also being a release build
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_kernel.dylib 0x1979faa60 __pthread_kill + 8
1 libsystem_pthread.dylib 0x197a32c20 pthread_kill + 288
2 libsystem_c.dylib 0x19793fa20 abort + 180
3 Python 0x1222357a8 fatal_error_exit + 16
4 Python 0x1222355fc fatal_error + 44
5 Python 0x122237b30 _Py_FatalErrorFormat + 228
6 Python 0x122237b4c _Py_FatalRefcountErrorFunc + 28
7 Python 0x122161114 none_dealloc + 28
8 Python 0x1221e6e90 _PyEval_EvalFrameDefault + 600
9 Python 0x1221f5848 _PyEval_Vector + 116
10 Python 0x122116260 method_vectorcall + 168
11 QtGui.abi3.so 0x137a96198 QSyntaxHighlighterWrapper::highlightBlock(QString const&) + 200
12 QtGui 0x107e8dce8 QSyntaxHighlighterPrivate::reformatBlock(QTextBlock const&) + 128
13 QtGui 0x107e8dc00 QSyntaxHighlighterPrivate::reformatBlocks(int, int, int) + 360
14 QtCore 0x1065f38f8 void doActivate<false>(QObject*, int, void**) + 1396
15 QtGui 0x107ea3bf4 QTextDocument::contentsChange(int, int, int) + 76
16 QtGui 0x107ea8940 QTextDocumentPrivate::finishEdit() + 124
17 QtWidgets 0x10775acdc QWidgetTextControlPrivate::setContent(Qt::TextFormat, QString const&, QTextDocument*) + 1180
18 QtWidgets.abi3.so 0x1529600d4 Sbk_QPlainTextEditFunc_setPlainText(_object*, _object*) + 140
19 Python 0x12215e3d0 cfunction_vectorcall_O + 92
20 Python 0x1221f1070 _PyEval_EvalFrameDefault + 42040
21 Python 0x1221f5848 _PyEval_Vector + 116
22 Python 0x122116260 method_vectorcall + 168
23 libpyside6.abi3.6.6.dylib 0x123870860 PySide::SignalManager::callPythonMetaMethod(QMetaMethod const&, void**, _object*, bool) + 540
24 libpyside6.abi3.6.6.dylib 0x12387041c PySide::SignalManager::SignalManagerPrivate::qtMethodMetacall(QObject*, int, void**) + 760
25 QtCore 0x1065f3664 void doActivate<false>(QObject*, int, void**) + 736
26 QtCore 0x1067b9298 QItemSelectionModel::emitSelectionChanged(QItemSelection const&, QItemSelection const&) + 216
27 QtCore 0x1067b8e80 QItemSelectionModel::select(QItemSelection const&, QFlags<QItemSelectionModel::SelectionFlag>) + 636
28 QtCore 0x1067b8b60 QItemSelectionModel::select(QModelIndex const&, QFlags<QItemSelectionModel::SelectionFlag>) + 68
29 QtCore.abi3.so 0x127920e4c Sbk_QItemSelectionModelFunc_select(_object*, _object*) + 732
30 Python 0x12215db40 cfunction_call + 100
31 Python 0x122112e58 _PyObject_MakeTpCall + 128
32 Python 0x1221f11c4 _PyEval_EvalFrameDefault + 42380
33 Python 0x1221f5848 _PyEval_Vector + 116
34 Python 0x122113174 _PyObject_FastCallDictTstate + 208
35 Python 0x12217d030 slot_tp_init + 188
36 Python 0x1221754dc type_call + 136
37 Python 0x122112e58 _PyObject_MakeTpCall + 128
38 Python 0x1221f11c4 _PyEval_EvalFrameDefault + 42380
39 Python 0x1221f5848 _PyEval_Vector + 116
40 Python 0x122114e34 object_vacall + 228
41 Python 0x122115084 PyObject_CallFunctionObjArgs + 44
42 binaryninjaui.abi3.so 0x151939320 std::__1::__function::__func<Sbk_UIAction_Init(_object*, _object*, _object*)::$_0, std::__1::allocator<Sbk_UIAction_Init(_object*, _object*, _object*)::$_0>, void (UIActionContext const&)>::operator()(UIActionContext const&) + 76
43 libbinaryninjaui.1.dylib 0x106bd93e0 UIActionHandler::executeAction(QString const&, UIActionContext const&) + 296
44 libbinaryninjaui.1.dylib 0x106bd9390 UIActionHandler::executeAction(QString const&, UIActionContext const&) + 216
45 libbinaryninjaui.1.dylib 0x106bd9390 UIActionHandler::executeAction(QString const&, UIActionContext const&) + 216
46 libbinaryninjaui.1.dylib 0x106c4358c CommandPalette::itemClicked(QModelIndex const&) + 576
47 QtCore 0x1065f3694 void doActivate<false>(QObject*, int, void**) + 784
48 QtWidgets 0x1077d2818 QAbstractItemView::activated(QModelIndex const&) + 52
49 libbinaryninjaui.1.dylib 0x106c41e1c CommandList::keyPressEvent(QKeyEvent*) + 192
50 QtWidgets 0x1075af82c QWidget::event(QEvent*) + 488
51 QtWidgets 0x107632a98 QFrame::event(QEvent*) + 56
52 QtWidgets 0x1077d0db4 QAbstractItemView::event(QEvent*) + 484
53 QtWidgets 0x10756716c QApplicationPrivate::notify_helper(QObject*, QEvent*) + 272
54 QtWidgets 0x1075681c0 QApplication::notify(QObject*, QEvent*) + 1036
55 QtCore 0x1065a9774 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 292
56 QtWidgets 0x1075c3248 QWidgetWindow::event(QEvent*) + 180
57 QtWidgets 0x10756716c QApplicationPrivate::notify_helper(QObject*, QEvent*) + 272
58 QtWidgets 0x107567fac QApplication::notify(QObject*, QEvent*) + 504
59 QtCore 0x1065a9774 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 292
60 QtGui 0x107c83bd8 QGuiApplicationPrivate::processKeyEvent(QWindowSystemInterfacePrivate::KeyEvent*) + 252
61 QtGui 0x107cdf1a4 QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 408
62 QtGui 0x107cded90 QWindowSystemInterface::flushWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 524
63 libqcocoa.dylib 0x10568dcbc -[QNSView(Keys) handleKeyEvent:] + 1832
64 libqcocoa.dylib 0x10568ebb4 -[QNSView(Keys) keyDown:] + 92
65 AppKit 0x19b493fec -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 480
66 AppKit 0x19b493c38 -[NSWindow(NSEventRouting) sendEvent:] + 284
67 libqcocoa.dylib 0x105696f84 -[QNSWindow sendEvent:] + 860
68 AppKit 0x19bb59e70 -[NSApplication(NSEventRouting) sendEvent:] + 1604
69 libqcocoa.dylib 0x105637510 -[QNSApplication sendEvent:] + 76
70 AppKit 0x19b7a78cc -[NSApplication _handleEvent:] + 60
71 AppKit 0x19b35bcdc -[NSApplication run] + 512
72 libqcocoa.dylib 0x1056435b8 QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 2124
73 QtCore 0x1065b3458 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 540
74 QtCore 0x1065a9e00 QCoreApplication::exec() + 112
75 binaryninja 0x104094a88 0x104034000 + 395912
76 dyld 0x1976aa0e0 start + 2360