I have the same issue after the macOS upgrade, with 2 diferent wireless headphones (Bose QC 35 II, and AirPods gen 2). The connection simply drops in the middle of a call, or I break out and no one in the call can hear me properly.
To be mentioned that all works ok on my iPad and iPhone, no connectivity issues there with either of the headsets.
I tried everything, removed all existing bluetooth devices and added them back again, removed the bluetooth files from Library, reset the SMC.
I see some suggestions here that the new AirPLay receiver is causing interferences in Bluetooth connectivity with headphones and other peripherals.
I tried to remove it from System Preferences -> Sharing, but I don’t even have Air Play Receiver (i think my model does not support it: MacBook Pro 2015).
This is becoming very frustrating, anyone else found another solution/workaround for older gen macs?