UIToolBarContentView hides UIToolbar in iOS 11

In iOS 11 I found that elements of my UIToolbar are unresponsive.

When comparing view hierarchy where UIToolbar is placed into between iOS 10 and 11, I found out that UIToolBarContentView stays above UIToolbar and therefore prevents elements of UIToolbar to be tapped - it's highlighted with blue color on the image below.

Any ideas why UIToolBarContentView appears in front of UIToolbar in iOS 11 and prevents from interacting with it?

Thanks!