Rickshaw Stream Chart Vertically Misaligned

Question

A Rickshaw Stream chart (area chart in offset:wiggle mode) can look amazing with a large dataset, but with a smaller dataset it tends to stray wildly from its central horizontal axis. Any ideas why this is, or how to prevent it?

Example:

Demo: http://jsfiddle.net/xDZZJ/

var graph = new Rickshaw.Graph( {
    element: document.getElementById("chart"),
    renderer: 'area',
    offset: 'wiggle',
    height: 100,
    width: 500,
    series: data
    } );
graph.render();