T22 - One way audio for internal call to SCCP phone

[jst68]

I am using FreePBX to operate my phones. Everything is working fine with receiving and making outside calls. Furthermore, all internal calls, with the exception of one scenario, are working fine as well.

The only scenario that isn't working is a call from T22 phone (SIP) to a Cisco phone (SCCP). It only has one way audio (no audio from the Cisco phone) when the T22 calls the Cisco phone.

Should I assume that it is a Yealink issue since it is working with the Siemens Gigaset? Calls between the Yealink and Gigset phone work fine though...

Oddly, enough everything also works fine when the Cisco phone calls the T22.

I have been playing around with a lot of settings, but I cannot figure out what the issue.

Is somebody here successfully using the same scenario? Any tips?

Thank you!