I have a problem with terrain and I don't know how to fix it

So basically I am making an open world game but after making a lot of parts of the map I just saw that there is a tiny part of terrain outside of the world. I see that there is something because when I select the terrain in the explorer and press F it does not center the map but it shows me the map and in the center is nothingness.

This is how it looks when I press F:

Do you know an easy way to fix this? Any plugins?

btw I can’t find the terrain part with my eyes. Do you know a plugin that highlights terrain? Or anything else that could help?

i spent a lot of time with replacing materials in a selection box, but nothing was worth it.

i only had to restart studio

rip one hour of lifetime

This is a studio bug, generally just terrain being weird.
It’s similar to terrain randomly appearing above places it shouldn’t be when you are far away, and correcting when you are closer.