Going to try to loosen and realign the whole unit from underneath the shelf area. I think you can access it via the trunk? Otherwise, consider adding a large piece of metal to weigh down the shelf. Just don't let if fly forward and smack you in the back of the head when you slam your brakes.
The QuattroWorld website is not affiliated with or endorsed by Audi AG or
Audi of America, Inc. AudiTM, QuattroTM, Avant,
Tiptronic, FrontTrak, A2, A3, A4, A6, A8, S3, S4, S6, S8, TT, TT-S, R8,
RS4, RS 6, Q7, Q5 and allroad quattro are trademarks of Audi AG.