Change bone Z position on root bone in Unreal 5.2.1 animation

Question

I’ve import an old animation, but it has a wrong root bone Z position (set to 90 instead of 0, to touch the floor not to floating…). When I set it to 0, everything works, the full animation works well with the character touching the floor in Z 0. But when I save all, close and reopen, the animation return with z bone 90.0. I’ve tried also to export and reimport it but without success. Where am I wrong?