What is XY size of the landscape in the World Machine? You will need to adjust XY scale in the unreal as well to make it match to Word Machine.
For example:
if landscape in WM has size 2x2km with heightmap resolution 2017 then unreal XY scale will be 200000/2017 = 99.15
for Z size (elevation) in WM = 1000m, z scale in unreal will be 100000/65535*128 = 195.3
65535 is a range of values for 16bit heighmap
128 is unreal internal Z scale for heighmaps