In case caller or callee can not hear ring back and they have 183 in packets, early media has been set in local remote side.In order to hear ringback, we can either ignore early media or generate ring back from SBC if its software SBC.
To ignore early media we can either set ignore_early_media=true or ignore_early_media=ring_ready on dial plans.
Lets say we have issue on incoming calls from Carrier ( inbound calls ), so call hits external profile and uses dial plan that reach out the internal side.
So we should add it on this dial plan. Export variable should be set before bridging.