After you mentioned that your ESC’s have linear BEC I was not sure if that would solve the issue as its the switch mode BEC’s that can cause inteference with one another. You said you are using Afro ESC’s and I know of a buch of people having sync issues with these ESC’s which is what I think the issue is. Are you using SimonK or BLheli firmware on your ESC?
In terms of checking if it is a sync issue you can look at the logs and inspect the RC_out commans send from your pixhawk to the ESC. If the RC out is all over the place then the problem is likely that pixhawk has some sensor issues and is sending strange commands to the motors. Otherwise if the RC_out is smooth according to your throttle inputs then the issue is likely something with the ESC. If you dont know how to look at the logs check out the quick guide on how to analyse Pixhawk log files.
Let me know how you get on, but I feel that using latest BLheli firmware should fix the issue as that is what other users report. I myself dont have loads experience with AFRO ESC’s as we dont sell them yet. I have only used some with a miniquad powered by a flip32+ board but did not have any issues.