The ac vents inside the car have become loose, anyway to fix this without replacing the vents?

 

I had the same thing. Replaced the entire piece under warranty. On and earlier car that this happened to I built up the freiction points a little bit with hot glue from a glue gun (behind where you cant see it, and careful to not glue two pieces together). On our cars the dealer showed me that the piece is just a pullout piece.

 

I just pulled and reinstalled mine, due to replacing the center-front console. Mine were fine.

But .. you two live in very hot places! Und Deutschland ist nicht so heiss! So maybe they aren't familiar with making long-term, dimensionally stable plastics there.