The view debugger reveals what’s going on with this bug. The contents of the navigation bar are being copied. Here’s what the navigation bar looks like before you show the search:
And here’s what it looks like afterwards:
The two replicant views and the extra UILabel are the problem. I don’t know what they’re doing there and I can’t find a way to remove them.
EDIT By the way, I think some of Apple’s apps display the same bug. It’s easier to see if you have large titles, because then you can see the large title and the extra label at the same time: