Potential-induced degradation (PID) is a prevalent concern in current commercial photovoltaic technologies, impacting their reliability, with the mechanistic basis for PID in perovskite photovoltaic technologies being poorly understood. Here, we investigate the PID mechanism in perovskite minimodules. Our findings reveal nonuniform degradation in the photoluminescence intensity and spectral blue shift. After 60-h laboratory PID stress tests at −1500 V and 60°C, device efficiency drastically decreases by 96%, and the shunt resistance decreases by 97%, accompanied by a significant quantity of Na+ ions (derived from the soda lime glass) throughout the device structure, leading to a typical PID-shunting effect. Interestingly, we observed a rapid recovery of device performance during room-temperature dark storage, in which Na+ ions located close to the glass substrate side rapidly migrated out of the device. Moreover, we also found that the Na+ ions do not appear to diffuse through the grain boundaries but rather their neighboring area and grain interiors, judging by microscopic conductivity mappings.