Was having some issues with a Yealink T41s receiving call from both external and internal. Hours of troubleshooting later what I thought was a codec issue turned out to be an issue with the phone RTP Encryption being set to true which is its default setting.
edit: Adding: Originate Resulted in Error Cause: 88 [INCOMPATIBLE_DESTINATION]
edit: Adding: Originate Resulted in Error Cause: 88 [INCOMPATIBLE_DESTINATION]