My Mercedes failed inspection and one of the mängel were a hair crack in the housing of the side mirror, reason being that moisture could go inside and kill the LEDs. The main fault was a rusted wheel axle support that held up everything in the rear, Mercedes replaced it for free however (3,500 Euros!!) but had to pay for a brake line repair that TÜV didn't see but at least they listed the hair crack as a fault!