I'm really sad because that beta firmware (20180308, on my C1200 v2) didn't solve the reboot problem. I also done the method of factory reset and reconfigure, but the router keeps rebooting at least...

@CarlosFigueira I have the same issue, my router rebooted 8 times last day (2020. 06. 17.) Did the new beta firmware helped you out? Should I try it the firmware update on my C1200 V2?