Hi, I need help with a Retell AI call issue. One of my phone numbers intermittently fails when calling into Retell AI. The call reaches Retell AI’s SIP endpoint but is immediately rejected with: SIP 486 – Rejected USER_BUSY Another number, using the same Telnyx account but a different SIP connection and a different agent, works normally. The failing onetime works immediately after being re-added, but later starts returning SIP 486 again. This also happens when tested with a new agent and a new account. Could you please advise: * What typically causes SIP 486 (USER_BUSY) on calls? * What steps should I check or reset to fix this issue? Thank you. @Omar Ashraf | Community Lead @Colin - Integrations @ Retell AI @Shah - support @ Retell AI