A further update from the experiments on 2020-10-05. In short, I have not seen an issue today.
I have repeated multiple times running the Camera app and the Microsoft Teams video preview, and the image has displayed each time. I have tried restarting Windows and still did not see an issue today.
This is all positive, but I do not know what has changed to improve things. I expect it will make sense to close this ticket soon as things stand.