Sound problems when streaming from vMix to Zoom meeting using NDI

In a professional studio I am using vMix for production. With NDI I stream the sound and video to another computer that is in Zoom meeting.

The problem is that the sound is NOT uniform. Sometimes attendees can hear well and a minute later  a lot of them report that the sound is low. I heard the recording from the vMix machine and it is just fine.

So, during the Zoom meeting I clean the checkbox: "Automatically adjust microphone volume" (in the computrer where the microphone set to NDI) - It helps for a while, but than again, attendees complains about the low sound, so I marked the checkbox "Automatically adjust microphone volume" and the attendees wrote that the sound is better, but after a while, while I did nothing, they wrote that the sound is low!?!?

Any idea how to fix this issue?

Thx

Zohar Amihud