app_conference: No translator path from unknown to unknown

Hello,
I am wondering if anyone can tell me why app_conference fills my logs with these warnings.

It doesn’t seem to matter what codec I am using.

Also, it was my understanding that if you had two parties in a conference and both were the same codec app_conference wouldn’t do any transcoding, however my “show g729” shows 2/2 encoders/decoders in use.

Thanks.