Camera zoom varies unpredictably on Ubuntu

[dorinho]

I run Zoom 5.17.5 on Ubuntu 22.04.4 to attend online lessons.
When I connect, everything is fine, but when the teacher switches between different modes (e.g. by sharing her screen or establishing breakout groups) it has unpredictable effects on my camera's zoom settings. Rather than the nice view of me in my study, it switches to showing a corner of the ceiling, or a close-up of my front teeth. Sometimes a subsequent action by the teacher resets it, sometimes not.
I cannot find anything in the Zoom settings that allows me to control this, and low-level Linux commands such as v4l2-ctl -d /dev/video1 -c zoom_absolute=20 tend to make things worse rather than better.
Is there a simple "reset camera settings to default" somewhere? Or is this a known bug under investigation?

(It's also tricky to Google this given the name of the application)

[dorinho]

Camera is Logitech HD Pro Webcam C920 - guess I should have mentioned that - but I don't think it's the webcam's fault.