Thank you for writing.
I reviewed your project and can confirm that the memory is not released when calling the Dispose method. There are some complex references which have to be sorted properly when disposing the control and clearly these references are not handled correctly. I have added this to our Public Feedback Portal. You can track the progress if this issue, subscribe for status change alerts and add your vote/comment to it on the following link - Feedback item.
Until the issue is resolved the workaround you can apply is the one you have implemented where you clear the series before you dispose of the chart.
I have updated your Telerik Points
for bringing this issue to our attention.
I hope this will be useful. Should you have further questions, I would be glad to help.
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