That’s not the shutter-that’s interlacing artifacts in your video when you need to have your video rendered out to progressive scan.
Make sure your project settings match the video properties, which you can get Vegas to match automatically. Since it’s probably interlaced footage, in the project settings, set the De-interlace method to “Blended” or “Interpolated”. Blended is used on footage without much motion since you’ll see more blur from it with motion, so you might want to try Interpolated.
And when you render, render out to progressive scan and set de-interlace method to “None”.