The different behavior of RadChart when contained in StackPanel and Grid is caused by the differences in the measurement mechanisms of these containers. While the grid panel measures its children against the available space, the stack panel with vertical orientation measures its children against infinite height. What we would recommend you to do in this case is to set the Height property of RadChart to an appropriate value.
I will forward this issue to our developers to further investigate the issue and think of the possible ways to improve this behavior.
Your Telerik points have been updated. Thanks.
the Telerik team
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