When the material itself has begun to craze or spider-crack, polishing the surface cannot remove damage running through the lens.
Use close-ups in natural light plus a full-headlight view. Fine surface marks and damage running through the cover are not the same finding; a photograph alone should not be used to assert a measured crack depth or exact cause.
When the outer lens needs replacement, the assembly, housing and retained components still need assessment. Matching lenses are vehicle/headlight-specific and new repairs use VLTA-supplied parts, professional resealing and pressure testing.