From time to time, I notice that the HC4 looses its IP address. journalctl then tells me:
dhcp4 (eth0): selecting lease failed: -131
But I don't know the reason for it. Sometimes it happens after a reboot. Pulling the ethernet cable off and plugging it in again seems to help and after a few tries, the HC4 is reachable again.
I'd be happy to give more information, but I don't know yet how to debug it. I noticed that /var/log (zram) sometimes gets full but I don't know if this is related…