Hi Hamilton,
I have created a simple bar chart populated by observable items. I added a button to the app, so that when I click the button - an item increases its value. I do not get any flickering and the bar changes its size accordingly. I have attached this app for your reference.
If you keep experiencing issues with the RadChart, you can open a support ticket and attach a small project that we can run that reproduces this behavior so that we can try to find a way to avoid this flicker. For now I can only suggest you make sure the underlying items implement the INotifyPropertyChanged interface and that the collection they reside in implement the INotifyCollectionChaged interface.
All the best,
Petar Marchev
the Telerik team