Same issue. 75M line. Port forwarding correct. DNS correct. Randomly, phones will die ("URL call disabled") but the computer using the phone's switch is still online.
Ran QOS test with max # of connections while downloading a large file, just to add stress to the line.Upstream jitter 1.2 msDownstream jitter 0.5 msUpstream packet loss 0.0 %Downstream packet loss 0.0 %Upstream packet order 99.9 %Downstream packet order 99.9 %Packet discards 0.0 %MOS 4.1 REGISTER ms 534 msINVITE ms 541 msBYE ms 297 msTestRingCentral QoS
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