Trying setting force_send_socket(PUBLIC_IP:5060); in a branch route. Get redirects creates a new branch for each contact header returned in the 302 and you want to act upon those branches.
if (t_check_status("302")) { get_redirects("*"); t_on_branch("REDIRECT_BRANCH") t_relay(); }
branch_route[REDIRECT_BRANCH] { force_send_socket(PUBLIC_IP:5060); }
John