How do I create a smooth screen recording of me scrolling through my prototype? Using QuickTime results in the site being cutoff

I am trying to make recordings of me navigating through my prototypes so that I can upload it to my site. One recording will be a single scroll through a long page, and the rest is a multi-page prototype with clicking involved. What is the best way of doing this?

I was trying to use quicktime on Mac to record  my screen while I scroll through the single long page manually. Although I start at the top of the prototype when scrolling, the recording cuts off the top of the page and makes it appear as if I’ve scrolled about 400px down from the top of the page - which does not match what I saw at the time of recording. Can anyone assist with this?