Weird UVs issue on static mesh import

[Sneppy]

I’m experiencing some problems regarding mesh UVs.
In 3dsMax everything looks fine but once imported in Unreal some faces seem to have rotated uvs. I thought maybe I was doing something wrong, but I exported a higher resolution version (I simply applied “MeshSmooth” to the stack: EditablePoly > UnwrapUVW > EditPoly > Mesh Smooth) and the problem was gone:

http://s24.postimg.org/opkrnzvv9/Cattura_di_schermata_2.jpg

I also noticed that the low resolution version has some problems with smoothing groups, even though I properly set them up in 3dsMax and exported with “Export smoothing groups” option enabled:

http://s24.postimg.org/7nrxlwh05/Cattura_di_schermata_3.jpg

This are my UVs:

http://s24.postimg.org/havfvm9zp/Cattura_di_schermata_5.jpg

Any idea why this is happening? What did I do wrong?

[Sneppy]

Collapsing to editable mesh rather than editable poly solved the problem? Why? what’s the difference?

[haldolium]

How did your modifier stack look?

Sounds strange.

[Sneppy]

the stack: EditablePoly > UnwrapUVW > EditPoly > Mesh Smooth

I tried collapsing all, applying rest XForm, Mesh Smooth set to 0 but none worked (except converting to Editable Mesh). I reimported the .FBX in Max and found out that deleting the face and capping the hole solved the problem. Then I found this post (http://forums.cgsociety.org/archive/index.php?t-898928.html) where it says:

Basically, thou if you have a face that is not facing the same direction as the rest of the faces in your model it is because the face has been rotated, (not flipped, flipping a face reverses the normals, which is not what we want at all.)
Each polygon has its orientaion determined upon creation, so the easiest way to fix one polygon would be to delete the offending polygon and re-create the polygon taking care to ensure the correct orientation of the new polygon, on a four sided polygon it will assign the first created vertex to the lower left corner of your image and the last created vertex to the upper left corner of your image.

In my opinion that’s exactly what happened (this would also explain the smoothing groups problem). Converting to editable mesh maybe forces Max to recalculate (I actuallly have no idea what I’m talking about ) polygons orientation. Now I also tried reconverting to editable poly and the issue is gone.
If this is the case I just don’t understand why everything looked fine in Max before exporting.