I attach some information that I found reading issues in github. Maybe the problem is that the SDP fields are disordered.

This link talks about that problem but It was not solved:

https://github.com/espressif/esp-adf/issues/1133

We are developing a VOIP system with ESP-ADF and the project is working without relevant problems. We are testing the system with 2.7 ADF version, TekSIP 4.2 and MicroSIP software.

The problem start when we use one ATCOM VOIP phone. With MicroSIP and TekSIP we cannot see problems and when the ESP32 ...