RuntimeError: libpng signaled error

Sometimes I am getting this error with the trunk version. Not sure what a MWE would be. Has anyone encountered this?
Thanks, Chaffra

RuntimeError                              Traceback (most recent call last)
/usr/local/lib/python3.6/dist-packages/ipympl/backend_nbagg.py in _handle_message(self, object, content, buffers)
    178             self.manager.resize(w, h)
    179         else:
--> 180             self.manager.handle_json(content)
    181 
    182     def send_json(self, content):

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in handle_json(self, content)
    437 
    438     def handle_json(self, content):
--> 439         self.canvas.handle_event(content)
    440 
    441     def refresh_all(self):

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in handle_event(self, event)
    238         handler = getattr(self, 'handle_{0}'.format(e_type),
    239                           self.handle_unknown_event)
--> 240         return handler(event)
    241 
    242     def handle_unknown_event(self, event):

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in handle_draw(self, event)
    254 
    255     def handle_draw(self, event):
--> 256         self.draw()
    257 
    258     def _handle_mouse(self, event):

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in draw(self)
    151             super().draw()
    152         finally:
--> 153             self.manager.refresh_all()  # Swap the frames.
    154 
    155     def draw_idle(self):

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in refresh_all(self)
    441     def refresh_all(self):
    442         if self.web_sockets:
--> 443             diff = self.canvas.get_diff_image()
    444             if diff is not None:
    445                 for s in self.web_sockets:

/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_webagg_core.py in get_diff_image(self)
    199             buff = _png.write_png(
    200                 output.view(dtype=np.uint8).reshape(output.shape + (4,)),
--> 201                 None, compression=6, filter=_png.PNG_FILTER_NONE)
    202 
    203             # Swap the renderer frames

RuntimeError: libpng signaled error

ipympl の backend_nbagg.py と、matplotlib の backend_webagg_core.py における handle_draw()、refresh_all()、get_diff_image() を通る処理経路、特に traceback に示されている _png.write_png の呼び出しから始めます。報告されている Python、ipympl、matplotlib、libpng のバージョンで失敗を再現し、その後、エラーが発生しなくなったことを示す最小例と回帰テストのカバレッジを定義します。