Hey Nat,
Thanks for getting back to me.
I tried opening the second window just now, dragging the red cursor across the preview shows exactly how I want it to look. It's just clicking play seems to cause it to stutter and not work.
I'll try and do what Borate suggested an upload my file to see what's going on.
I'm using V8.56. The bulk of the video is just >30fps gaming footage with a few google images flying by. AMD RYZEN 7. 16GB Ram. 500Gb (Asus Zepherus G14)
https://www.dropbox.com/sh/wgujz7gvkzr0sxa/AABZKfQDw27Yk4uUvQrSQFg_a?dl=0
Hope this had uploaded okay, as I say it's just my first week using VP so I'm aware my project is a little shonky, but I really appreciate the help.