Hi there, @zerohoon! Replacing the battery was a great call. This certainly is the best step and should not have resulted in a quick drain again. I recommend swapping this Contact Sensor with another one in the home that does not have this concern. Then check both Contact Sensors to see if the one you swapped is behaving the same way with its battery draining. This will rule out signal and environmental factors.
Otherwise, the best solution will come from our support team. Please give our support team a call at one of the numbers available here. We’re taking additional steps to protect our team and help reduce the spread of COVID-19, so this has resulted in longer than normal wait times. If you are outside of the US, please read our response to COVID-19 here to see how to contact support.