I suppose that these issues are related to the mentioned bug reports - if you use ClearSelection() method, it does not work properly, so the selected points of the chart would remain. In this case if the user selects another data point, SelectionChanged will be raised to un-select the previously data point and in this case SelectedPoints collection will be empty.
I've raised the priority of both issues related to selection and hopefully, we'll manage to provide a fix soon.
I am sorry for any inconvenience caused.
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