Animation import. Strange error

Hello everyone.

I have a problem with importing animation from fbx file. I made a first person weapon setup in 3dsMax with skinned weapon and hand models.
Skeletal meshes were imported without problems, both for hands and the weapon. They have same scale and same basic skeleton.

Here’s a picture of whole weapon rig without hands model

But when i want to import the animation for weapon skeleton im getting this error

I triple checked bone names, everything match cause they’re both exported from same .max file, biped rig and weapon rig are linked to the root bone.
I used very similar setup in my previous projects for UE4 and it worked flawless.

I checked bake animation and resample all in fbx export settings. Im using 2014 version of 3dsMax with it’s default fbx plugin.
Both 4.3.1 and 4.7.2 versions of Unreal Engine are giving me this error.

Does anyone know what i’ve done wrong?

After hundreds of re-exports using diffrent settings i managed to fix it. My root bone was incorrectly named, re-naming it from RootNode to just Root fixed the problem.