Model with bones animation from 3Ds MAX

I have a model that I’m trying to import into my scene. This model has an animation with bones. I’m doing these steps below:

Exporting Bone-based Animations
There is a procedure you should follow when you want to export bone-based animations:

Set up the bone structure as you please.
Create the animations you want, using FK and/or IK
Select all bones and/or IK solvers
Go to Motion->Trajectories and press Collapse. Unity makes a key filter, so the amount of keys you export is irrelevant
“Export” or “Export selected” as newest FBX format
Drop the FBX file into Assets
In Unity you must reassign the Texture to the Material in the root bone.

But the model appears with the normals flipped. Whats could be the problem?

So to recap the comments into an answer:

Ideal workflow:

Reset transforms and check Normals BEFORE you apply skin and rig > Validate exported FBX in Max first

Troublshooting workflow:

Validate your exported FBX in max first > use normal tools to isolate flipped normals > Submit a case if this does not find the problem

I made a test today:

I added all the bones to the object without adjust them. It works in scene. But when I adjust the envelops in the object, it happens again and the normals are flipped.

Why? It’s too weird