I think that I found a little button repainting bug:
I am calling setToggleState() on a DrawableButton with flag "dontSendNotification". As can be seen in the implementation of Button::setToggleState(), dontSendNotification causes the function sendStateMessage() not to be called. The problem is that this function is responsible for calling buttonStateChanged() which in turn updates the image to be used in the DrawableButton. So, disabling notifications also disables image updating in DrawableButton. I guess that this can be fixed by calling buttonStateChanged() -- but not ButtonListener::buttonStateChanged -- when dontSendNotification is set.