I did try changing the interpolation mode, but at the sporadic capture rate for that particular tag, it didn’t help. However changing from showing sampled data to raw data has resulted in a better representation (left - Sampled, right - Raw):
The only issue now is that the underlying JFreeChart component doesn’t pull in any data points that are outside of the chart window. So for sporadic data such as mine, there can be gaps created at either end of the chart as in the screenshot on the right as the previous/next data points can be outside of the chart range. Notice on the left that there is a gap mid-through 23 Feb for the light grey pen. A sampled display resolves this, but brings in issues of its own. There’s not really a win-win solution 