It can be reproduced only in .NET 6 project. It works in .NET Framework 4.8.

It is also reproducible with RadDropDownList. Once the drop down is opened, clicking anywhere on the form, outside the popup, doesn't close it.

Run the attached sample project and right click the button. If you click outside the popup, the drop down is not closed.

Expected: the popup shawl be closed.

Actual: the popup is not closed