Audio won't work for one app while screensharing

[EmmerichM]

We're doing some remote contact center training, and when some of our new agents are screensharing all computer audio shares except for the audio of the caller. It's not an issue for the trainers (when they share their screen, everything works including the caller's side).

Everyone's logged into a Zoom account, we've tried reinstalling Zoom (windows desktop app, we all have the most recent version), selecting both mono and stereo when screensharing, and using a different headset just in case it was interfering. Any other suggestions on how to fix this? If it helps, we use 8x8 for our phone system. For the contact center we have to use a client in-browser as well as their work app.