They are at fault for breaking this. I have done over 50 evaps in the 140...The only lock that I have seen break was when a tech got in the car with the dash out and used the lock as a handle to get out. When he put is weight on it, it broke free and we had to replace the lock and housing.
Sorry you have to go through this. I recommend to take Mercedes ONLY to repair shops with MERCEDES techs.
A/C shops usually work on everything and don't have the experience on Mercedes and make mistakes.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS