All six cameras drop network connection at same time. Guessing firmware - server heartbeat issue. TP Link unwilling to ack issue. Have mirrored camera lan traffic to wireshark but as yet unable to ID possible recurring trigger from network. Do see outgoing traffic from camera on fixed outside destination addresses/ports like time-etc that are dropped by firewall as they should be. TP Link support continues to claim no issue with their product. Ready to get refund on all six. Local network status shows no loss of connection before, during, or after cameras drop off the network. After power-cycle cameras reconnect and review of activity from storage shows cameras continued recording events without interruption. Sadly, this likely has a simple fix if the right person at TP Link was assigned to debug.