Primary WAN cuts during the Tokyo ISP window and the Edge pair flips to local survivability on 2024.6.1. R750 handsets handle the handoff fine, but the WebRTC softphone drops audio with STUN_BINDING_ERROR: 487 Request Terminated. BIOS telemetry shows the secondary NIC wakes up, but the routing table won’t catch the local media ports. Found a community thread where someone patched iceTransportPolicy to relay as a quick workaround. Network config looks clean. Console logs just spin on ICE_GATHERING.