@Astranger 

Try to turn off the WiFi connection on the door lock (remove the battery cover, you will see a WiFi ON/OFF switch), check whether the battery is still draining fast.

While the WiFi is off, you can still control the door lock locally via Bluetooth.

I would recommend performing the test at night while everyone is home, and leaving it overnight. Make sure to monitor the door lock's power consumption under normal conditions first, then you can make a comparison.