I have a problem with 3cx on premiss (windows v15.5). In an internal call between 2 devices, there is no audio in the first 2 seconds of the call. After the first 2 seconds the conversation goes well. This is with 2 ios phones, or with 1 ios phone and one yealink at an external location. If I do the echo test with * 777 I do not hear any delay. I use direct sip (stun-remote). The firewall test has passed. Does anyone have an idea?