Welcome to broken additional brake light owners club
1) My first light was broken. But they did not change it under warranty. They said someone tried to steal it and broke it. And my car would be the first car that the lamp would be changed. They did not know
how to change. So I bought and changed myself using elsawin. It is very easy.
2) Second light was broken again 2 months before. They did not changed it under warranty again. Because I changed ti myself not at service.
3) I bought the third lamp. I uninstalled the broken light and gave the third lamp to them. They installed. Now they know the continuum. They did it with registration. So if it happens again they will change in under warranty.
In Turkey it costs 30 pound including fitting in Seat authorized service.