I reset the preview RAM, i presume that was irrelevant.
Here’s what the recording details are, looks good to me: https://prntscr.com/clzn6g
I actually already had the Media Match selected, and i tried the = button which gave me the same preset i made that i usually use. MP4 12,000,000 avg. / 24,000,000 max two-pass, 320kbps AAC.
I tried disabling the Media Match and rendered again, using the same preset as always.
Worth mentioning that i have edited the video and rendered in Premiere using the exact same settings and it’s very smooth, so it’s definitely Vegas :(.
You can see the Premiere render here: https://www18.zippyshare.com/v/JGSlspTG/file.html