Using Voiceover with Sierra 10.12

I recently updated my MacBook Air to the latest operating system, Sierra 10.12. Since the download I am now struggling with using Voiceover in the way that I am used to.

Previously when using the rotor, working within documents, or when browsing a webpage, I could easily scroll down multiple lines by holding the down arrow key. Now it insists on reading the first part of every line I scroll past, which makes for a very slow process.

Is there a way of adjusting any settings in order to go back to what I am used to?

I am also finding difficulty when switching between windows, for instance from mail to safari, VoiceOver repeats the window i am on several times needlessly. Is there a way of stopping this?

Any other tips on how to maximise my Mac with Voiceover would be really appreciated.

Thanks.