Flask process randomly, consistently dies

[lewismc]

I am seeing many instances of the following whilst running the project over a Joshua language bundle

lmcgibbn@LMC-056430 /usr/local/joshua_translation_engine(PYTHON-3) $ python app.py -b /usr/local/joshua_resources/apache-joshua-es-en-2016-10-06 -s es -t en -p 5674
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
Exception in thread "main" java.lang.RuntimeException: Could not listen on port: 5674.
    at org.apache.joshua.server.TcpServer.start(TcpServer.java:61)
    at org.apache.joshua.decoder.JoshuaDecoder.main(JoshuaDecoder.java:80)

The Exception will result after a number of minutes and before around 10 minutes. Need to profile this to see why it is dying.