Not sure exactly what you mean by "crashes" but try resetting the AirPort Extreme. Perform a "hard reset" according to the following excerpt from Resetting an AirPort Base Station or Time Capsule FAQ:
- Press and hold the reset button with a pen or pencil until you see the status light (LED) start to flash amber rapidly, which should occur after about five seconds.
- Release the button, and the AirPort Base Station or Time Capsule will hard reset.
That's all anyone would do at an Apple Store, so try it yourself before going there to obtain a diagnosis.
You will need to configure all its settings again as if it were new.