How to switch back to autofocus while recording video?
Solution 1:
I don't believe that there is a way to force it to autofocus but it will re-focus if you don't touch it again.
From Apple Support:
Your camera automatically focuses the image and adjusts the exposure based on what you’re pointing it towards. That way, you always start with a brightly lit photo. You can change the camera focus and exposure to a specific area. Before you take the photo, tap the place on the screen that you want to adjust. If you want to keep the focus and exposure in the same spot, press and hold on the screen until you see AE/AF Lock.