RadMultiColumnComboBox - Dropdown stays open even after window is closed

[Shawn]

I have a custom control that uses RadMultiColumnComboBox and when it's used in a dialog window, and the user opens the dropdown, then without clicking on anything else but the X to close the dialog window, the window closes but the drop down stays open. I would like to fix this in the control itself instead of on the screen if possible but everything I try doesn't work. I've tried adding a .CloseDropDown() call to the LostFocus, Unloaded, and even listened for the parent window to close and all of those attempts had no effect. This seems like a bug in the RadMultiColumnComboBox. I do have KeepDropDownOpen set to False.

[Martin Ivanov]

I've tested this with the latest version of Telerik UI for WPF, but couldn't recreate the problem. Can you check the attached project and let me know what I am missing?