Update: No backups I have correct this issue, it happens the exact same way every time I load up my world, and I have not encountered it before this... In fact I used to travel through this corrupted part before, as I have markers up for when I did...

Update 2: The corruption isnt just in the nether, it is affecting my overworld at these coordinates too... You can see that with the screenshot below... I can try opening the world in a beta to see if it works.... I will update how that goes... The corruption in the overworld is enormous being 25000 blocks long and on average 300 blocks wide...

I looked through and didn't find a report on this so, my bad if there is already a thread but my nether chunks have gotten corrupted pretty bad... I have a backup but this really needs fixed, just entire chunks of my world cut out.... 

It was caused by the 1.16 update since it is apparent that the terrain is 1.16...

I can however download my old backup and test these coords to see if they work...

Im not exactly sure how to cause it Im sorry, however this is pretty bad...

Video for what I am talking about: https://youtu.be/-MkmG58hVxM