The symptoms clearly point to a hardware-level signal degradation issue, which is most commonly caused by a malfunctioning or damaged Wi-Fi antenna in the smartphone. CompTIA A+ mobile device troubleshooting emphasizes comparing the affected device's signal strength with other nearby devices. In this case, other devices in the same location have stronger Wi-Fi signals, meaning the network itself is functioning normally. The consistent low signal across multiple networks strongly suggests antenna failure.

Modern smartphones use internal antenna assemblies located along the frame or behind the back cover. If the antenna becomes loose, damaged, or obstructed, the device may show weak or unstable Wi-Fi connectivity, especially in crowded environments where strong, stable reception is required to maintain a connection.

Option B (outdated Wi-Fi standard) would limit speed but not cause significant signal weakness compared to surrounding devices. Option C (interference) affects all devices in an area similarly—not just one device. Option D (power settings) may reduce background activity or scanning frequency, but it does not cause consistently low signal strength.

Therefore, the most likely cause is a malfunctioning Wi-Fi antenna inside the smartphone.