iOS >11 UISearchBar broken animation while navigation push/pop

Number:rdar://6164844138987522 Date Originated:02.04.2019
Status:Open Resolved:No
Product:iOS SDK Product Version:>11.0
Classification:Bug Reproducible:Yes
Area: UIKit

 - UINavigationController’s stack,
 - 2 consequent UIViewControllers
 - both of them have UISearchBar (through setting navigationItem.searchController in viewDidLoad or viewWillAppear, doesn’t matter which method is used)

Steps to reproduce:
Option #1 (PUSH):
 - Run the app, pull down the search bar on the first screen
 - Push the second screen animated
 - Pay attention to the push transition
Option #2 (POP):
 - Run the app, push the second screen
 - Pull down the search bar on the second screen
 - Pop the second screen animated
 - Pay attention to the pop transition

 - SearchBar’s background is hanging over the content of the appearing screen until the transition is done, then the bar disappears without any animation
The bug is easily reproducable in the official WWDC application

 - FilesApp, strangely, does not have such a bug, it seems to have a completely customized NavigationBar (WHY THOUGH). It works perfectly, it must work this way everywhere. 
+ ability to pull the searchBar with scroll


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