As long as we do not switch to any other tab 'during' the test, it is not a problem.That maybe a reason but cant say 100 percent. When taking test, everything else should be closed. No tab, pdf or even notepad. I'll let others pitch in. Can you check the webcam resolution? When one takes the picture of the Id, does it show on the screen so we can take a clear picture? Maybe during the test your face was blurred? Did you do a webcam check by calling a friend to make sure it is clear?
It is most likely a connection issue or webcam issue or if he was not fully visible in the camera all through the test or someone else came in the frame during the test.