Switch 5 webcam bug with DirectShow

Switch SW512-52 Windows 10

I have tried to use the rear facing webcam with 2 different DirectShow packages - Yawcam and OpenCV

In both cases, when I get the settings pop-up and try to disable auto-focus, the manual focus (range 100 to 450) does not focus the camera (it just blurs more and more).
This can be shown with yawcam, where I get autofocus to focus very close up (a few centimetres), then disable autofocus. The image immediately goes out of focus and cannot be recovered no matter where I set the manual focus slider.

I think the camera is somehow misleading DirectShow and the 'focus' parameter on the slider is not really focus on the camera.

Any suggestions? I need to write a C++ windows app that makes use of the camera with manual focus. Currently the driver seems bugged.