Appears to be from the Fuel Tank Door...don't know if I should do something or not.

Volvo 850 1997, 165K miles Asking for advice about the clunking noise my door locks have started making when I lock the doors with a key. Only happens if I'm locking all 4 doors...not if only driver's door. Not sure if it's the door or fuel door. Don't imagine it's pertinent but...recently had brake...