I’ve just updated to iOS 11.1.1. Since updating, touch begin events now have a 2 second delay in the top 10% and bottom 10% of the screen. Touch events are fine for the center 80% of the screen.
I assume this is related to the top and bottom swipe areas where you can drop system menus on to the screen.
For the time being my fix is just to squeeze all of my UI buttons out of the offending areas.