Thanks for sharing the details. It's helpful to see the pings.
Can you try setting your Chunk Rate Limit to "Very Low"?
The data you shared shows a Peak of 1.26 Mb/s which is lower than the "Low" 8 chunk/s limit estimate of 2 Mbit. This might imply that the bandwidth of your connection is the limiting issue.
Try "Very Low" and let us know if this helps.
Please share a screenshot with the debugging enabled if it happens again when on "Very Low".
Can you also share the output from: http://www.speedtest.net/