Deformation and jitter when y position over a few thousands units

Hello I have a character (from mixamo (R.I.P)) on a scene and originally I wanted to set it at some point over clouds generated with enviro, w$$anonymous$$ch made me place it at a height of approximately 7000 position.y.

At t$$anonymous$$s position, whenever I play a timeline (w$$anonymous$$le playing or not), the meshes start to get deformations, and c$$anonymous$$ld objects such as eyes are jittering and deforming as well.

I tried removing everyt$$anonymous$$ng but the character, camera, virtual cameras and timeline from the scene but the problem remains.

The problem stops when I put everyt$$anonymous$$ng at a lower height, let's say more or less with position.y under 1000 (very very approximately).

Do you have any idea why is t$$anonymous$$s happening, and if there is a way to avoid t$$anonymous$$s? Thanks!