I fixed one that broke at the main joint and it held for several months before I replaced it.



1. I applied some glue to the broken joint and reseated the parts on the car to retain the proper position.



2. I cut some thin aluminum flashing and formed/bent it over the glued joint. I kinda bent it like this: _/\_.



3. The metal should be as close to the plastic as possible. I slathered epoxy around it and let it cure.



4. Reinstall it but you still must be careful.



BTW: I 've had them snap and blow right off. They cost $75 and it is another $75 to paint by code.