The IsBusy property of RadBusyIndicator does not correctly reflect the value of its data-bound source when the control is unloaded and then loaded again while using a OneWay binding.
A common scenario where this occurs is when RadBusyIndicator is hosted inside a TabItem of a TabControl:
The binding is not re-evaluated when the control is loaded again, resulting in the control displaying a stale value that is out of sync with the bound ViewModel property.