Terrain Drops with a straight border forming

This ticket is invalid as it relates to a modded or 3rd party client/server.

• Any non-standard client/server build needs to be taken up with the appropriate team, not Mojang.

• Any plugin issues need to be addressed to the plugin creator.

• This site is for addressing issues related to the base unmodded Minecraft.

I have no mods I'm trying to figure out why I see random drops from like y75 to 62. There is a terrain bug

Please.attach a screenshot

Well actually it looks like a loading chunk

Screenshot ?

This is an example