Same here most of the time, although a few times it has actually worked.
Backtrace (without debug symbols)
#0  0x00007fffe725e590 in ?? ()
#1  0x00007ffff011bcee in _XIOError () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#2  0x00007ffff0118fb2 in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#3  0x00007ffff01197e9 in _XFlush () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#4  0x00007fffdc294cf6 in ?? () from /usr/lib/nvidia-367/libGLX_nvidia.so.0
#5  0x00007fffdc22941d in ?? () from /usr/lib/nvidia-367/libGLX_nvidia.so.0
#6  0x00007fffd711e098 in ?? () from /usr/lib/nvidia-367/libnvidia-glcore.so.367.57
#7  0x00007fffd70e2469 in ?? () from /usr/lib/nvidia-367/libnvidia-glcore.so.367.57
#8  0x00007fffd70e42bb in ?? () from /usr/lib/nvidia-367/libnvidia-glcore.so.367.57
#9  0x00007fffdc2d02fa in ?? () from /usr/lib/nvidia-367/libGLX_nvidia.so.0
#10 0x00007ffff7de7c35 in _dl_fini () at dl-fini.c:240
#11 0x00007ffff28e0ff8 in __run_exit_handlers (status=1, listp=0x7ffff2c6a5f8 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true) at exit.c:82
#12 0x00007ffff28e1045 in __GI_exit (status=<optimized out>) at exit.c:104
#13 0x00007fffe72655e2 in ?? ()
#14 0x00000000006692c0 in ?? ()
#15 0x00007ffff78e3189 in ?? () from /usr/lib/x86_64-linux-gnu/libKF5XmlGui.so.5
#16 0x00007ffff358193c in QCoreApplicationPrivate::sendThroughApplicationEventFilters (this=0x7fffffffb260, receiver=0x7ffff35ada19 <QObject::event(QEvent*)+233>, event=0x6692c0) at kernel/qcoreapplication.cpp:1081
#17 0x00007ffff471389c in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x6692c0, e=0x6692c0) at kernel/qapplication.cpp:3799
#18 0x00007ffff471b296 in QApplication::notify (this=0x7fffffffce40, receiver=0x6692c0, e=0x7fffe00039a0) at kernel/qapplication.cpp:3556
#19 0x00007ffff3581cf8 in QCoreApplication::notifyInternal2 (receiver=0x6692c0, event=event@entry=0x7fffe00039a0) at kernel/qcoreapplication.cpp:988
#20 0x00007ffff35843bb in QCoreApplication::sendEvent (event=0x7fffe00039a0, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#21 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x65bd50) at kernel/qcoreapplication.cpp:1649
#22 0x00007ffff3584828 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1503
#23 0x00007ffff35d4e13 in postEventSourceDispatch (s=0x6ae690) at kernel/qeventdispatcher_glib.cpp:276
#24 0x00007fffed5d71a7 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007fffed5d7400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#26 0x00007fffed5d74ac in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#27 0x00007ffff35d521f in QEventDispatcherGlib::processEvents (this=0x6a4ed0, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#28 0x00007ffff357fcea in QEventLoop::exec (this=this@entry=0xa5b020, flags=..., flags@entry=...) at kernel/qeventloop.cpp:210
#29 0x00007ffff38c7cc2 in QBasicDrag::drag (this=0x69ecd0, o=<optimized out>) at kernel/qsimpledrag.cpp:193
#30 0x00007ffff38e3df9 in QDragManager::drag (this=0xa73750, o=o@entry=0xa57fe0) at kernel/qdnd.cpp:141
#31 0x00007ffff38e2737 in QDrag::exec (this=this@entry=0xa57fe0, supportedActions=..., defaultDropAction=defaultDropAction@entry=Qt::IgnoreAction) at kernel/qdrag.cpp:284
#32 0x00007ffff38e27e7 in QDrag::exec (this=this@entry=0xa57fe0, supportedActions=..., supportedActions@entry=...) at kernel/qdrag.cpp:240
#33 0x000000000041c3ec in SpectacleCore::doStartDragAndDrop (this=0x7fffffffce90) at /workspace/build/src/SpectacleCore.cpp:283
#34 0x00007ffff35ace76 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffb9e0, r=0x7fffffffce90, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:130
#35 QMetaObject::activate (sender=0x70bad0, signalOffset=<optimized out>, local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3723
#36 0x00007ffff35ace76 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffbaf0, r=0x70bad0, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:130
#37 QMetaObject::activate (sender=0x6ffa00, signalOffset=<optimized out>, local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3723
#38 0x00007ffff35ace76 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffbc00, r=0x6ffa00, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:130
#39 QMetaObject::activate (sender=sender@entry=0x702af0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3723
#40 0x00007ffff35ad4b7 in QMetaObject::activate (sender=sender@entry=0x702af0, m=m@entry=0x63ea20 <KSImageWidget::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3602
#41 0x000000000042bb80 in KSImageWidget::dragInitiated (this=this@entry=0x702af0) at /workspace/build/obj-x86_64-linux-gnu/src/moc_KSImageWidget.cpp:125
#42 0x000000000042353c in KSImageWidget::mouseMoveEvent (this=0x702af0, event=<optimized out>) at /workspace/build/src/Gui/KSImageWidget.cpp:80
#43 0x00007ffff475a398 in QWidget::event (this=this@entry=0x702af0, event=event@entry=0x7fffffffc0c0) at kernel/qwidget.cpp:9144
#44 0x00007ffff484076e in QFrame::event (this=0x702af0, e=0x7fffffffc0c0) at widgets/qframe.cpp:550
#45 0x00007ffff471389c in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x702af0, e=0x7fffffffc0c0) at kernel/qapplication.cpp:3799
#46 0x00007ffff471bb35 in QApplication::notify (this=<optimized out>, receiver=0x702af0, e=0x7fffffffc0c0) at kernel/qapplication.cpp:3273
#47 0x00007ffff3581cf8 in QCoreApplication::notifyInternal2 (receiver=receiver@entry=0x702af0, event=event@entry=0x7fffffffc0c0) at kernel/qcoreapplication.cpp:988
#48 0x00007ffff471a85f in QCoreApplication::sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#49 QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x702af0, event=event@entry=0x7fffffffc0c0, alienWidget=alienWidget@entry=0x702af0, nativeWidget=0x70bad0, buttonDown=buttonDown@entry=0x7ffff4c15c30 <qt_button_down>, 
    lastMouseReceiver=..., spontaneous=true) at kernel/qapplication.cpp:2771
#50 0x00007ffff4774090 in QWidgetWindow::handleMouseEvent (this=this@entry=0x9f29f0, event=event@entry=0x7fffffffc4d0) at kernel/qwidgetwindow.cpp:613
#51 0x00007ffff4776863 in QWidgetWindow::event (this=0x9f29f0, event=0x7fffffffc4d0) at kernel/qwidgetwindow.cpp:239
#52 0x00007ffff471389c in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x9f29f0, e=0x7fffffffc4d0) at kernel/qapplication.cpp:3799
#53 0x00007ffff471b296 in QApplication::notify (this=0x7fffffffce40, receiver=0x9f29f0, e=0x7fffffffc4d0) at kernel/qapplication.cpp:3556
#54 0x00007ffff3581cf8 in QCoreApplication::notifyInternal2 (receiver=receiver@entry=0x9f29f0, event=event@entry=0x7fffffffc4d0) at kernel/qcoreapplication.cpp:988
#55 0x00007ffff38d30a0 in QCoreApplication::sendSpontaneousEvent (event=0x7fffffffc4d0, receiver=0x9f29f0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:234
#56 QGuiApplicationPrivate::processMouseEvent (e=0xa70750) at kernel/qguiapplication.cpp:1909
#57 0x00007ffff38d4fa5 in QGuiApplicationPrivate::processWindowSystemEvent (e=e@entry=0xa70750) at kernel/qguiapplication.cpp:1693
#58 0x00007ffff38b2e6b in QWindowSystemInterface::sendWindowSystemEvents (flags=...) at kernel/qwindowsysteminterface.cpp:654

*** This bug has been marked as a duplicate of bug 369404 ***