Terrain seams after using .raw heightmaps

Using a .raw I found online i was able to get two terrain tiles to connect fine. With my .raw files however it will connect to a neighbour terrain when the other terrain has no heightmap. But when i import a heightmap into the other terrain the edges will disconnect.

Does the Unity terrain need the .hdr file that you get with the .raw?

before applying heightmap to neighbour terrain:

After:

You can see it connects initially but after giving the second terrain it's own heightmap it disconnects. I am using .raw i generated with GlobalMapper.