Thank you for this image example, @Christian_Bailey! Just to confirm, despite the battery message and level resolving itself, you’ve checked that there is indeed not a low battery in your Smoke/ CO listener?
As a troubleshooting step, please remove the battery and then put them back in. If possible, please also replace the battery. This will rule out most variables. Please also check that your other Alarm devices are not reporting this, and that the distance between your Base Station and listener is not too great for health status reporting signals to be efficient. Feel free to let us know how this goes!