Updating the Terrain collider after importing raw terrain data?

I have 7 identical terrains that get loaded separately (they are populated with different textures and foliage to show different times of the year) I had to adjust the actual shape of the terrain, but wanted to keep all the texturing work.

I altered ONE terrain, how I wanted it, exported the RAW terrain data from the setting menu,, then imported it into all my 6 other scenes terrain.

THIS WORKED GREAT!

However, I needed to re-make some of my NPC waypoint paths. so I started that job.. but the points WERE NOT conforming to the new terrain...

Now I realise they are conforming to THE OLD terrain collider data---
and YES I have copied that new data into the collider slot!

HERES THE QUESTION! How can I throw away the old terrain data, and update it to what actually exists!

Thanks