Occasionally, when I do a double tap on a button to activate it with Voice Over, it will make the VO double tap sound but nothing will happen. If I go to another app and switch back to the current app, it fixes the problem. Does anyone know what may be causing this and how to stop it from happening? I believe it started about 6 months to a year ago. I'm not sure if it happened with IOS 11 or not. It isn't a big deal but it is mildly annoying. I am using an iPhone 6S, running IOS 12.3.