The touch area for the search button is off centre which makes it tricky to hit sometimes. In the screenshot I’ve got VoiceOver enabled, which shows the search icon is right-aligned in the touch area instead of centred.
Details to reproduce: Enabled VoiceOver and move the selection over the Search button. OS: iOS 13.3 Device: iPhone XR App Version: 3.14.0 #588
The box shows the ‘touch area’ where a user can click - as you can see on that device the box isn’t centred around the magnifying glass (the box doesn’t appear on your fun but it is, in essence, still there).
The box appears if you have VoiceOver enabled (for visually impaired users). It’s an easy way to pick up these kinds of layout issues without using the developer tools.