I honestly don’t know what’s the cause, and not knowing the polling frequency gives me little information about this ‘heartbeat’ app you are using. It could be due to your specific network setup. We just had a customer reporting network issue, and after diagnosis, it turns out it’s due to IP conflict (someone on the same network manually set a static IP that conflicts with OpenSprinkler’s IP). If you want, send it back to us and we can perform a thorough check to see what has caused the issue.