Here is the backtrace, I stopped it when it freezed
Spoiler:
* thread #1: tid = 0x56c7, 0x00007fff9f7e4c86 libsystem_kernel.dylib`__psynch_cvwait + 10, stop reason = signal SIGSTOP
frame #0: 0x00007fff9f7e4c86 libsystem_kernel.dylib`__psynch_cvwait + 10
frame #1: 0x00007fff9f8ce96a libsystem_pthread.dylib`_pthread_cond_wait + 712
frame #2: 0x00000001001823e1 Python`PyThread_acquire_lock + 113
frame #3: 0x0000000100187347 Python`lock_PyThread_acquire_lock + 71
frame #4: 0x0000000100148e8f Python`PyEval_EvalFrameEx + 30591
frame #5: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #6: 0x00000001000ccb7c Python`function_call + 364
frame #7: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #8: 0x00000001000b4136 Python`instancemethod_call + 182
frame #9: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #10: 0x00000001000a1787 Python`PyObject_CallFunctionObjArgs + 359
frame #11: 0x0000000100148450 Python`PyEval_EvalFrameEx + 27968
frame #12: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #13: 0x00000001000ccb7c Python`function_call + 364
frame #14: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #15: 0x00000001001495eb Python`PyEval_EvalFrameEx + 32475
frame #16: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #17: 0x000000010014db25 Python`fast_function + 117
frame #18: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #19: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #20: 0x000000010014db25 Python`fast_function + 117
frame #21: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #22: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #23: 0x00000001000ccb7c Python`function_call + 364
frame #24: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #25: 0x00000001000b4136 Python`instancemethod_call + 182
frame #26: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #27: 0x000000010014d31d Python`PyEval_CallObjectWithKeywords + 93
frame #28: 0x00000001065480e8 QtCore.so`PyQtSlot::call(_object*, _object*) const + 40
frame #29: 0x0000000106547fe5 QtCore.so`PyQtSlot::invoke(void**, _object*, void*, bool) const + 309
frame #30: 0x0000000106548967 QtCore.so`PyQtSlotProxy::unislot(void**) + 103
frame #31: 0x00000001065488e5 QtCore.so`PyQtSlotProxy::qt_metacall(QMetaObject:: Call, int, void**) + 85
frame #32: 0x000000010608dca9 QtCore`QMetaObject::activate(QObject*, int, int, void**) + 2777
frame #33: 0x000000010547ab7a QtWidgets`QMenu::popup(QPoint const&, QAction*) + 314
frame #34: 0x000000010547bafe QtWidgets`QMenu::exec(QPoint const&, QAction*) + 78
frame #35: 0x00000001054bcc44 QtWidgets`___lldb_unnamed_symbol2585$$QtWidgets + 2004
frame #36: 0x00000001054bd854 QtWidgets`___lldb_unnamed_symbol2589$$QtWidgets + 388
frame #37: 0x000000010608dd82 QtCore`QMetaObject::activate(QObject*, int, int, void**) + 2994
frame #38: 0x00000001053f345d QtWidgets`___lldb_unnamed_symbol1130$$QtWidgets + 45
frame #39: 0x00000001053f4091 QtWidgets`QAbstractButton::mousePressEvent(QMouseE vent*) + 337
frame #40: 0x00000001054bcfc0 QtWidgets`QToolButton::mousePressEvent(QMouseEvent *) + 400
frame #41: 0x0000000105347f27 QtWidgets`QWidget::event(QEvent*) + 1607
frame #42: 0x00000001053f3f13 QtWidgets`QAbstractButton::event(QEvent*) + 179
frame #43: 0x00000001054bd6b4 QtWidgets`QToolButton::event(QEvent*) + 324
* frame #44: 0x000000010530942b QtWidgets`QApplicationPrivate::notify_helper(QObje ct*, QEvent*) + 251
frame #45: 0x000000010530cc5d QtWidgets`QApplication::notify(QObject*, QEvent*) + 9421
frame #46: 0x0000000104ffe0cf QtWidgets.so`sipQApplication::notify(QObject*, QEvent*) + 127
frame #47: 0x000000010605d423 QtCore`QCoreApplication::notifyInternal(QObject*, QEvent*) + 115
frame #48: 0x0000000105309dbb QtWidgets`QApplicationPrivate::sendMouseEvent(QWid get*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) + 987
frame #49: 0x0000000105368570 QtWidgets`___lldb_unnamed_symbol622$$QtWidgets + 1200
frame #50: 0x000000010536777f QtWidgets`___lldb_unnamed_symbol617$$QtWidgets + 111
frame #51: 0x000000010530942b QtWidgets`QApplicationPrivate::notify_helper(QObje ct*, QEvent*) + 251
frame #52: 0x000000010530c80e QtWidgets`QApplication::notify(QObject*, QEvent*) + 8318
frame #53: 0x0000000104ffe0cf QtWidgets.so`sipQApplication::notify(QObject*, QEvent*) + 127
frame #54: 0x000000010605d423 QtCore`QCoreApplication::notifyInternal(QObject*, QEvent*) + 115
frame #55: 0x0000000105950b39 QtGui`QGuiApplicationPrivate::processMouseEvent(QW indowSystemInterfacePrivate::MouseEvent*) + 2185
frame #56: 0x000000010594f9c3 QtGui`QGuiApplicationPrivate::processWindowSystemE vent(QWindowSystemInterfacePrivate::WindowSystemEv ent*) + 131
frame #57: 0x000000010593c59a QtGui`QWindowSystemInterface::sendWindowSystemEven ts(QFlags<QEventLoop::ProcessEventsFlag>) + 346
frame #58: 0x000000010c297371 libqcocoa.dylib`___lldb_unnamed_symbol458$$libqcoc oa.dylib + 33
frame #59: 0x00007fff8a17e981 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOU RCE0_PERFORM_FUNCTION__ + 17
frame #60: 0x00007fff8a15fa7d CoreFoundation`__CFRunLoopDoSources0 + 557
frame #61: 0x00007fff8a15ef76 CoreFoundation`__CFRunLoopRun + 934
frame #62: 0x00007fff8a15e974 CoreFoundation`CFRunLoopRunSpecific + 420
frame #63: 0x00007fff896eaa5c HIToolbox`RunCurrentEventLoopInMode + 240
frame #64: 0x00007fff896ea799 HIToolbox`ReceiveNextEventCommon + 184
frame #65: 0x00007fff896ea6c6 HIToolbox`_BlockUntilNextEventMatchingListInModeWi thFilter + 71
frame #66: 0x00007fff87c905b4 AppKit`_DPSNextEvent + 1120
frame #67: 0x00007fff8840ad6b AppKit`-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:deque ue:] + 2789
frame #68: 0x00007fff87c84f35 AppKit`-[NSApplication run] + 926
frame #69: 0x000000010c29625d libqcocoa.dylib`___lldb_unnamed_symbol440$$libqcoc oa.dylib + 2189
frame #70: 0x000000010605ab1d QtCore`QEventLoop::exec(QFlags<QEventLoop::Process EventsFlag>) + 381
frame #71: 0x000000010605d9fa QtCore`QCoreApplication::exec() + 346
frame #72: 0x0000000105032bd0 QtWidgets.so`___lldb_unnamed_symbol6360$$QtWidgets .so + 80
frame #73: 0x0000000100148e8f Python`PyEval_EvalFrameEx + 30591
frame #74: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #75: 0x000000010014db25 Python`fast_function + 117
frame #76: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #77: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #78: 0x000000010014db25 Python`fast_function + 117
frame #79: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #80: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #81: 0x000000010014db25 Python`fast_function + 117
frame #82: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #83: 0x000000010014dbc2 Python`fast_function + 274
frame #84: 0x0000000100148a85 Python`PyEval_EvalFrameEx + 29557
frame #85: 0x0000000100141402 Python`PyEval_EvalCodeEx + 1538
frame #86: 0x00000001000ccb7c Python`function_call + 364
frame #87: 0x00000001000a6f33 Python`PyObject_Call + 99
frame #88: 0x000000010014d31d Python`PyEval_CallObjectWithKeywords + 93
frame #89: 0x00000001000938f5 calibre-launcher.dylib`run + 1221
frame #90: 0x0000000100001dfe calibre`main + 158
frame #91: 0x0000000100001d54 calibre`start + 52