ZigBee device never reports offline/unavailable

I have a couple of SNZB02D temperature and humidity sensors which periodically (quite often actually) stop reporting in. One is currently showing that the last termperature update was 9 days ago yet in the device info/zigbee info panel it shows as last seen a few minutes ago. Looking in the log around that time there is nothing referring to this device.
I have an automation that will send me a notification listing off line devices but these sensors never show up. Several other Zigbee devices do show as off line when they stop reporting.
Any ideas anyone?

The integration should have the settings to set timeout for battery and mains powered devices.