I’m not familiar at all with World Creator but when inside World Machine you’ll notice the 0,0 is in the bottom left of your heightmap.
This is a +X,+Y origin.
When you import a terrain to UE4 you will notice when you click on a terrain, the translation widget appears in the top left. This is because UE4 uses a +X,-Y coordinate system. This is also why you have to flip the green channel sometimes when importing normal map textures if they were created in, or created for, an app that uses positive Y coordinates.
So this is why in World Machine I leave the Flip Y-Axis Orientation unchecked. It’s just easier for me in terms of work flow to work in World Machine with settings that match the program’s native workflow.
I’m 99 percent sure that this is what your problem is. The first time I imported a tiled terrain that is what my landscape looked like and it was the Flip Y issue.