Share Sound/ Optimze Video creates huge echo for MAC users

[cmagerEVI]

Hi!  My MAC using colleagues and I are all experiencing the inability to share sound or optimize video for sharing for a couple months now.  All updates are complete.  A huge echo is created for everyone in the meeting.   We absolutely cannot use these functions anymore.  We are all in different countries with different Zoom accounts. Zoom support has not given sufficient answers via email and I suspect this is not just a problem for my colleagues and I with MACs.  Anyone else have this problem and have found a solution?