To reproduce, just launch taurustrend2d --demo
cpascual@pc218:~$ taurustrend2d --demo MainThread INFO 2016-07-18 17:47:11,578 TaurusRootLogger: Using "PyQt4" for Qt MainThread INFO 2016-07-18 17:47:11,684 taurus.qt.qtgui.icon.icon: Setting Tango icon theme (from /tmp/kkt4/usr/local/lib/python2.7/dist-packages/taurus/qt/qtgui/icon/) Traceback (most recent call last): File "/tmp/kkt4/usr/local/lib/python2.7/dist-packages/taurus/qt/qtgui/extra_guiqwt/tools.py", line 264, in items_changed self.activate_command(plot, self.action.isChecked()) File "/tmp/kkt4/usr/local/lib/python2.7/dist-packages/taurus/qt/qtgui/extra_guiqwt/tools.py", line 247, in activate_command item.scrollRequested.disconnect(self.onScrollRequested) TypeError: 'instancemethod' object is not connected