Yes, i’ve seen this before. When the call is forwarded from RingCentral, it’s usually a media routing / conference bridge issue. The outbound leg is connected, but the audio stream Vapi listens to isn’t properly attached so it never detects human speech and transferSuccess doesn’t fire. Since it works when calling the Vapi agent directly, that confirms it’s likely, the SIP / RTP not passing correctly from RingCentral or One-way audio due to NAT or codec mismatch, RingCentral using a conference bridge that isolates media streams. To solve this, make sure audio codec is standard (PCMU/PCMA), Disable any “early media” or custom call handling in RingCentral, Test bypassing forwarding (direct SIP trunk if possible), Confirm Twilio isn’t putting the call into a separate conference room before transfer. I can help you properly trace the SIP + media flow and fix it cleanly.