X-Axis rotation irregularities in World Editor?

So I have a flat terrain mesh I've imported into BeamNG but it's giving me a very bizarre problem.

Basically, what happens is no matter what I do, BeamNG always forces the X Rotation axis by 0.056 degrees no matter what I do. I can test this by placing water down. Towards the end of the terrain, it's always submerged. By placing a plane to simulate water in Blender, I can see the terrain is completely 100% level. By rights, there's no reason at all it should appear submerged towards the end of the terrain.

In other words, BeamNG doesn't appear to allow complete zero-ing of the X-Axis rotation. Is this somekind of a bug with World Editor by any chance? I've checked the rotations in Blender and everything (rotation/position) is all 0,0,0. Looking at mesh's in the official maps, I can see they technically have the same problem but it's a non issue as they are significantly smaller than the scale of the mesh's I'm working with.

I have a terrain (New York) that's many miles long and it's causing a serious problem in the sense that the end of it is always submerged. I'm having to raise the terrain out of the water to compensate for it.