bone Transform misplaced in Unity

Hello everyone, on 3.5.7, I have a problem that is ruining my animations : the bones transform of my character's fingers aren't at the right place. The model is rigged using a biped with 3DS Max. as you can see on the image below, I select the base of the character's index, and the transform isn't at the right place. The gap is only on the Z axis, and occurs on every fingers of this particular character.

When reimporting the model on 3DS Max however, the bone is at the right place...

On this gif, you can see the finger :

• with its original rotation

• rotated 90° counter clockwise

• rotated 90° clockwise