I get kicked immediatly when I load into my server. All I get is "InsideTerrain Violation Level 200" in my console.

Seems like you're spawning under the map, likely a map issue.

or maybe in vanish when you went offline and the server had restarted.

it thats the case as soon as you wake bind noclip to stop yourself falling and being kicked immediately.

I got in the same situation by trying to tp to an old coord, only way i got out of it was to use RustAdmin to teleport me to an existing saved coord and wait for name to come up as joining and then click on tp, took a few tries but it worked

I used https://umod.org/plugins/terrain-violation-fix and granted the permission via rcon when I had the problem when using vanish.
Newest version of Vanish now just keeps you invisible even after you logout, so the teleport under map is deprecated.