Rendering issue (IMPORTANT)

There are specific parts of my world (Created in 20w16a) which are not rendering correctly for myself or other players.

It seems as soon as I enter the adjacent chunk, it renders as normal, however when I stand away you can see-thru the world.

Please see the images attached.

VIDEO ATTACHED GIVES A VERY GOOD VISUAL EXAMPLE -  Very sorry about the video compression quality, It wouldn't let me upload anything higher.