@smugleafdev poor/bad reception will drain the battery and it sounds as if you do not have enough Zigbee Router devices to extend range/coverage of your Zigbee network so devices need to re-send messages and thus draining battery, therefore before you do any further troubleshooting read and try to follow these tips → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Zigbee depends heavily on mesh networking and only most but not all main-powered products act as Zigbee Router devices, while no battery-powered act as Zigbee Router devices.