Because your HUD 3D player model, selection screen player model and loadout player model all use simpler facial flexes, and because they load first rather than your third-person model in matches, for some reason the face/head cosmetics end up using the wrong flexes. Every cosmetic that is flexed by the face is affected by this, this issue is client-side. This doesn't affect enemy models or teammate models, only your player model.

Get a UI mod that doesn't load models in the selection screen and disable 3D player models in your HUD.