RadContextMenu will be closed when you click outside of it or when you click on one of its RadMenuItems. If you have added a button inside RadMenuItem, when you click it, you have to manually close RadContextMenu by setting its IsOpen property to false, as you have mentioned in your post.
Hope this helps. Feel free to contact us in case you have any problems or concerns.
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.