Worldmachine Terrain Distortion around Edges

I’ve imported my terrain from worldmachine, and there it looks like this:

In engine, while it is mostly right, you will notice that there is distortion around the edges:

I can work around this (ie making the world big enough that the edges are never seen by the player), but is there a way to avoid this?

Note that it seems to happen regardless of terrain scale, but is more noticeable at higher Z scales.