Whenever I load in a world in a server, it corrupts it. Any block from the mod I placed it turned into something else/waterlogged some out of thin air

Terrestria is a mod that must be installed on both the client and the server since it adds custom blocks and other content. You almost certainly forgot to install it on the client.

If you still see this issue after installing Terrestria on the client, send an F3 screenshot and a log file.

Also, this isn't actual permanent corruption, but rather a simple desynchronization between the client and server.

I doesn't let me in the world without it in my mod files, so I had to have it installed on both clients. I hope this is what you meant by an F3 screenshot