Just restored a backup to a new server and I’m getting one way audio at any extension that uses ilbc. The extension sends audio but cannot receive. Also, when doing an echo test, I am unable to hear the prompt.
That is probably it. Maybe a regression and that is why it worked previously. If you can use chan_pjsip for your extensions, you should get ilbc to work correctly again.
Or you can try submitting a ticket to Asterisk.