The Infamous Log Error Code

I've been monitoring a run of 50 populations concurrently, looking at the logs periodically, and this is what I'm seeing:

2014-06-18T16:53:01.837453+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/u?data=20%20.02%2010.305194%2011.645005%200.176168%20-7.471089%20-8.742053%20-10.637163" host=infinite-harbor-9903.herokuapp.com request_id=ee1e7c15-6aa3-4087-923d-ad9d5b96f93b fwd="130.127.48.28" dyno=web.1 connect=1ms service=13943ms status=503 bytes=0

However, at the end of the previous run, I was seeing

2014-06-17T19:10:52.632445+00:00 heroku[router]: at=info method=GET path="/u?data=20%20.02%20-5.780477%20-7.264415%2011.783255%2015.508600%20-19.862916%2028.477992" host=infinite-harbor-9903.herokuapp.com request_id=b8587f93-92dc-424b-a2c0-2c4f6e0a2a41 fwd="130.127.48.28" dyno=web.1 connect=2ms service=16824ms status=200 bytes=172

This could mean that at higher concurrent run counts the GA does not initially receive results (perhaps the it is closing connections early), but then near the end, in the last few generations, it starts to receive results again. This could potentially explain the strange results we have been seeing.