Ring 2 recordings are all blank, but snapshot recordings are fine

One of the Ring 2 doorbell units is showing motion events, but has now been recording blank videos, where the video is all black screen. This would seem like a failure of the camera, except the periodic snapshots recorded show up perfectly fine in the timeline. This has been happening for months now apparently, and I can only rely on the snapshots to see anything from this unit, as even the live view is nothing but a black screen. Is this a common issue? I've got three others on the same account and they're working as they should. Is there different hardware involved between video recording vs still recordings for snapshots? Is this unit now defective?