This article explores modern community safety issues through a case of a building door in a residential area that cannot be automatically locked. Property management and residents attach great importance to safety issues, but frequent malfunctions of building doors have raised concerns. The property manager implemented increased patrols and monitoring measures, but a dispute arose between the security guard and the delivery guy over the door lock issue. The police revealed the door lock malfunction through monitoring and experimentation, while also pointing out that the delivery guy did not follow the operating procedures. In the end, both parties reached a settlement and the building doors were repaired, emphasizing the importance of following rules and timely maintenance.