Thank you for the attached project and explanations. I was able to quickly reproduce the faulty behavior. It appears that you do not have to zoom in to get this glitch, you can resize the chart and when the axes change their step and range, the second series seems not to get notified and it uses the old axis range to render.
The RadChart is the old charting solution and we have not made any changes to the code in the last three years. Our efforts are focused on the new ChartView which has a much better overall performance, it is very flexible and easy to set up. I suggest you completely remove the Charting.dll reference and switch to the new chart.
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