I had this issue with a USB headset.
Symptoms were microfreezes with entire game, and first 2 seconds of vox audio not sending.
Tested using a 5 count (1,2,3,4,5) and not hearing numbers (1,2) and tuning vox radio 5 to my GAMEID.
I switched to using a usb soundcard and any 3.5mm plug headset.
No more issues.