When a new iPhone screen is displayed, the screen header should be read. This worked correctly in iOS 10. iOS 11 does not say the screen header when voice over is on.
When the screen is loaded, The heading starts to read, but before it completes, "back button" is read.
Example. screen has a "back button" and a header of "Add New Account".
Voice over will read "Add back button". It the reading speed is set fast enough the full title will be read.
The issue seems to be that the app is not waiting for the header to complete reading before reading the next field.