Weird webcam problem: Losing sound connection in the middle of a call

I have a weird problem with my webcam (Logitech C170, running on a Windows 10 machine). The webcam has an integrated camera, and I use that camera to connect to video conferences (the webcam is connected to the computer via USB, there is no separate connection via the audio jack). What happens is that even when the audio connection works fine at first, in the middle of a call the input audio connection (i.e., for the microphone feed coming from me) breaks down for no apparent reason, and I turn silent for the other participants (although my mike is unmuted). The audio output (the audio feed coming from other meeting participants) continues to work fine, and so does the video connection, both input and output.

It seems this is not a hardware problem, as the microphone has worked fine at first and also works when I test it with a local audio recording. What is more, the same problem exists when I connect a different microphone that I hook up to the PC via the audio jack; the connection to that microphone will also work at first but then fail during a call for no apparent reason. When I go to the audio settings screen of the video conference software and then manually select the other microphone, that one will work at first but then fail later. This gives me a workaround - just switch to the other microphone when the problem occurs, and I will have that other mike functioning for a few minutes. But obviously this is not a long term solution.

The problem exists in two different video conference softwares that I have used (Zoom and Cisco Webex), so it can’t be a glitch on the software side of these. In addition, it has persisted both before and after I updated my operating system from Windows 10 1903 to 2004. I doubt it’s a driver problem, since it arises, as mentioned, with two different microphones. My best guess is that it is my antivirus software/security suite (Kaspersky) somehow interfering with access to the microphone, but I have tried settings in this regard too.

Does anybody have an idea what this might be, or what I can do to fix it? I’d be happy to buy a new webcam, but I doubt that’s the root cause.