Ah yes, great point. That should be more common in CGNAT or mobile networks than home/office networks. Although I don't know what residential ISPs are up to th

Ah yes, great point. That should be more common in CGNAT or mobile networks than home/office networks. Although I don't know what residential ISPs are up to these days. No doubt some sketchy practices have crept in. For that matter, it could be a low-RAM (carrier-provided?) NAT gateway (or very high network activity) at the premises, blowing up the NAT table. Still, could be fixable. If the application protocol has some kind of keepalive heartbeat, or if local hardware can be configured or upgraded.