Smoke Alarm Randomly Beeping

BRK SC9120BA chirps every couple of minutes with free flashing. 9v battery reads 9.3V on clot meter. I disconnected power (battery and ac) for 10mins or so and issue still persists. What am I missing?

BRK SC9120BA chirps every couple of minutes with free flashing. 9v battery reads 9.3V on clot meter. I disconnected power (battery and ac) for 10mins or so and issue still persists. What am I missing?