The audio is slightly off from the highlighted word on the screen. What's wrong?

This can happen when you use a Bluetooth headset, because there is often a slight delay for streaming audio wirelessly. The delay is particularly long when using built-in iOS voices. (The built-in iOS voices, while free and convenient, do have a number of issues that we cannot work around.)

If you want to use a Bluetooth headset, please use one of the premium voices such as Sharon or Heather. Alternatively, you can use wired earbuds or headphones.