When a face 3D model breaks during skinning, it’s usually from incorrect weight painting, faulty vertex binding, or topology incompatible with the rig.
Weight painting errors (uneven bone influence on vertices) cause stretching or tearing. Wrong vertex-bone links can make parts detach. Poor mesh topology—not optimized for facial movements (like around eyes or mouth)—fails to deform smoothly.
To fix it, use tools like Blender’s Weight Paint mode to adjust vertex influences or simplify the mesh, focusing on smooth transitions between bone areas.