XPS 15 9510, only one IR emitter flashing

WIndows Hello facial recognition on my laptop recently stopped working. I deleted the saved face and tried to set it up again, but the setup gets stuck on "make sure your face is centred in the frame" and "keep looking at the camera", with a white grid round my face. It doesn't go any further.

I can see only the left side IR emitter is flashing during setup, I'm sure there used to one on the right too.

If I look in device manager, I can see two devices under Cameras, listed as Integrated Webcam, both are using the Microsoft Usb Video Device driver.

Any idea if this sounds like an issue with the IR camera using the wrong driver, or perhaps one of the IR emitters is now fried?