The Repair Man
So she called a repair man.
The repairman comes and sees that indeed, the door falls out every time when a bus passes by.
"OK, I am gonna see what is going on, just close the door behind me" and he steps into the closet.
At that time the husband comes from work, opens the closet and finds the repairman.
Husband: "What the hell are you doing here!"
Repairman: "Well, you are not going to believe it, but I am waiting for a bus!"