I've already entered the system there, but unfortunately it didn't help.
We'll do a trace and check the codec and the media stream. Thanks for the info. Is there perhaps an old guide for an SBC SIP example ? It would be interesting to see what is configured there. The gigaset DECT as a SIP client can probably handle the MPS, that's no problem at all. The SBC was connected as a trunk not as a client. I suspect that MPS is a little different here too.