I similarly still can't get this to work, as of Beta 7.

Ziqiao, I was placing it in a UIVisualEffectView with vibrancy because in beta 4, if my symbol was a standalone UIImageView in the custom view, it didn’t get the default effect. I think this was one of the same beta 4 bugs that @KeithB was seeing. But now 

I can tell you that in beta 5, a UIImageView alone in the custom view finally behaves appropriately. It because unnecessary to embed it in the additional UIVisualEffectView with vibrancy and just put it in the custom view alone as you suggested, @DTS Engineer. Thanks.