Clio 197 Headlight Intensity

My Clio 197 failed MOT the other day on the below (headlamp intensity). This happened last year as well but the same garage replaced the bulbs and said it was sorted. Any ideas what could be causing this?

Headlamp light intensity severely reduced (4.1.4 (a))
I just replaced both on mine for the same reason, on the xenons and the projector ones its the “mirror” behind the lens that is burned out, so less light from the bulb gets reflected