ZOOM VoiceEngine Volume keeps resetting to 0 on Ubuntu 18.04

I'm lecturing with Zoom and Impress (Libreoffice) on Ubuntu 18.04.

The Ubuntu (really Gnome) Sound/Applications panel has two ZOOM VoiceEngine sliders. The top one controls what I hear from the remote side. The bottom microphone slider is no problem it just stays where I set it. The top one goes back to zero from time to time, seemingly when I switch windows.

How can I lock the top one down?

I did notice one pattern on my workstation. When a student adds or leaves the zoom the slider goes to zero. There may be other triggers but that one is consistent.

However, in another new experiment I tried running zoom on the Ubuntu workstation against Zoom on a Ubuntu laptop. When the host is on the workstation, the bad behavior shows. When the workstation is the client and the host is on the laptop no bad behavior. Same version of zoom.

I don't know what could be different on the workstation to cause the problem.

Go to Zoom setting. Under Audio, drag 'Output Volume' bar to Max level to keep zoom audio loud.

I've recently noticed this, too. The closest thing I could find was a post from 2018 to fix a similar issue where the volume kept getting set to 100%, and that it looks like was fixed in the 2019-12-01 release. I didn't have a ~/.pulse/daemon.conf file, and /etc/pulse/daemon.conf indicated that flat-volumes was already set to the default of no, but I uncommented it anyway. I haven't had a Zoom meeting since, so I'm not sure this will have done anything... I'm doubtful that it did, but might as well give it a shot.

i've had this problem too. i think i have solved it for myself but i have yet to test it on live zoom meeting with others. what i did was to go into zoom settings and then audio settings, increased the volume to max and unticked/unchecked the box that says "Adjust microphone volume automatically". this seemed to keep my microphone from resetting itself back to 0. i've only tried this by setting up my own meeting with me as the only participant but it seemed to work for me at least. i am using pulse audio by the way.