What happened in fact was that a graphics plotting function for
monitoring got called twice frorm a different thread, due to an 'old'
instruction inadvertently left. Due to the quasi random nature of the
incoming data streams, this happened rather very sparingly. As the
plotting itself involves quite a bit of code, there are probably
several if not many reasons why problems could arise. It was never my
intention to reenter this function and make it thread safe. Problem
I was indeed a surprise for me to see Python quit this way.
Thanks again for your commentary.