I just get to know today in a post about permanent prerender videos.
So I tried this on a fresh project without any transition or effect.
it is giving weird results.
please take a look.
thankyou.
This is a known problem - https://www.vegascreativesoftware.info/us/forum/v22-is-it-normal-for-selective-pre-render-to-change-colour--147312/#ca925970
Instead, try rendering from the Render As process applying the loop function until the problem is fixed.
A similar problem existed with the clipboard snapshot. I found a way to temporarily "fix" the issue on a per project basis. The "fix" for the snapshot problem seems to work for the prerender problem. It's the View Transform option in project settings causing problems. https://www.vegascreativesoftware.info/us/forum/clipboard-split-screen-showing-wrong-colour--146825/#ca922205