Sharp edges on landscape heightmap

Hi,
I’m trying to create a map using the heightmap created in the world creator, but they end up with these sharp edges … I tried to increase the resolution of the landscape from 63 to 256 but the results still weren’t good enough, I also tried tiled landscape with world composition, but I couldn’t change the landscape resolution (engine crashes when I try to change it, I think I’m doing something wrong) and ended up with the same results…