Map LODs look weird even at 99% static mesh details percentage

I’m creating a tiled map which I exported from world machine.
Problem is, when I try to generate LODs, here’s what I get:
It essentially tries to simplify that mountain line. The thing is, I set the simplification for this LOD at 99%. Heck, I even tried 100% and this thing still happens.
Now, this it’s actually supposed to look:

What am I doing wrong?

Please, let me know if there’s more information that would help analyze it.
Thanks in advance!