Skinning problem : Character deformed when imported in unity

Hello everyone,

I just imported a rigged, skinned, and animated character in maya on Unity 2020.3.5 HDRP, but his chest is deforming too much at every animation.

It looks like the problem is from an IK bone to stretch/squash the character, but I don't know how to fix it.

I tried different parameters of export (Maya) and import (Unity) but absolutly nothing change, but the pose is working without the skin.

This is the same deformation for every animation, and the problem is the same in different projects with different versions.

Maya


Unity (don't pay attention to the eyes/mouth lol)