For those having the same issue, you can fix it by making sure the child window (detail in this case) is completely independent of any other window. Set the owner of the child window to null. I suppose this is some issue related to the Owner/Owned relationship that I don't really have time to dive into. I don't think it is anything CM is doing - especially after looking at the WindowManager source and seeing non-CM examples of similar behavior on StackOverflow. Unfortunately, I need to use CenterScreen instead of CenterOwner.
dynamic settings = new ExpandoObject(); settings.WindowStartupLocation = WindowStartupLocation.CenterScreen; settings.ResizeMode = ResizeMode.NoResize; settings.Owner = null; settings.ShowInTaskbar = true;