Is the 3CX Server Hosted and where? Hosted with AWS (EC2 - t3.micro)
IP Phone Make/Model/Firmware No phones, only web apps
Trunk Provider Local trunk provider
Has the Firewall Checker passed: YES
Are custom Phone Templates being used: NO
Wireshark dump attached.
It happens both on the 3CX mobile app, as well as calling our number from a regular line. The sales team is connected using the web app / plugin in the Edge browser. Desktop app for Windows 10 is not yet ready I was told.
Just checked your capture, it does show a 2-3 second delay, but it is between the Ringing and the Okay, so that's means the delay is happening pre-audio.
Can you try the following:
If you have recordings enabled, disable them.
Dial *888 (which will request a callback), answer it, does the delay exist?