This is really weird. I had this happen a few times as well. I am not able to reproduce it though. What I did when this occured the last time:
I created a mesh in Blender, exported it (Using the same preset I always use for fbx), imported it to UE4 as LOD.
Now it was rotated 90 degrees, so because I didn’t find a fix for it (Tried importing it several times), I went back to Blender, rotated it the in the opposite direction as a temporary solution, exported again, imported again and it was fine.
Then later, (I did NOT export the mesh again from Blender, it was the same file), I imported it again (As LOD for the same object), and for some reason it was imported the correct way (Note: Correct = The same as in Blender, which in this scenario was rotated 90 degrees).