Camera works fine, except it won't transmit video in Teams

This problem is baffling me completely, and I've worked in IT Application support for almost 40 years. I hope someone can help me resolve it. A family member has a very important family court hearing to attend via Teams in a few weeks so I'd like to help her out.

This is a Lenovo laptop (Ideapad 330S-14IKB) with a built in SunplusIT webcam. The camera works perfectly in Google Meet and Zoom, but not in Teams. I can see my own video feed on my screen but the other Teams meeting users cannot see my image. The camera is enabled in Teams.

Some things I have already tried: 

• Updated webcam driver from Windows
• Updated webcam driver directly from Lenovo site
• Ensured Windows 11 is up to date
• Checked privacy settings to ensure Teams app is permitted to use camera
• Uninstalled any other apps (e.g. Zoom, Skype) that may be using the camera
• Cleared Teams cache folders and restarted
• Uninstalled and reinstalled Teams
• Performed a partial Windows reset, retaining user data
• Performed a full Windows reset, erasing the hard drive

Some other symptoms and things I've noted

• Camera works fine on my own Teams window and I can see my own image
• Camera transmits video correctly when the other party is on Android
• Camera stops transmitting video when other party is using Windows
• The same problem occurs using Teams in a browser web app, with either Edge or Chrome
• Screen sharing works fine
• Camera works fine in Google Meet (web) and Zoom (app)
• The problem persists if I log into the laptop with another user account
• The laptop has a fresh install of Office 365

What on earth is happening and what else can I try?

I'm very technical but this has beaten me!