Some picture thumbnails aren't generated

Some more info.

This seems to lock the back button too and I get the following traceback. I've attached a .png of the directory.

  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/controller.py", line 168, in prev
    self._select_from_ui_index(prev_ui_index)
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/controller.py", line 163, in _select_from_ui_index
    self.center_at(image_frame)
TypeError: center_at() takes exactly 3 arguments (2 given)
Traceback (most recent call last):
  File "edje.c_edje_object.pxi", line 59, in edje.c_edje.signal_cb (edje/edje.c_edje.c:7765)
  File "/usr/lib/python2.6/dist-packages/terra/ui/screen.py", line 77, in cb
    end_callback(self, old_view)
  File "/usr/lib/python2.6/dist-packages/efl_utils/callbacks.py", line 31, in cb
    end_callback(finished)
  File "/usr/lib/python2.6/dist-packages/terra/ui/window.py", line 425, in inform_end
    end_callback(self, sub_view_old, sub_view_new)
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/main/controller.py", line 546, in cb
    end_callback()
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/multitask/task/controller.py", line 231, in end
    last.unref()
  File "/usr/lib/python2.6/dist-packages/terra/core/controller.py", line 77, in unref
    self.delete()
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/controller.py", line 964, in delete
    self.thumbler.stop()
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/thumbnailer.py", line 147, in stop
    self.delete()
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/thumbnailer.py", line 140, in delete
    self.pipe.close()
  File "/usr/share/canola/plugins/canola-core.zip/canola-core/images/thumbnailer.py", line 185, in close
    os.close(self.fd_r)
OSError: [Errno 9] Bad file descriptor