Now I had chance to watch the stream on the second link: http://www.cosmosplus.com/space-station-camera-2 when the camera hasnot any light. I put here part of the screenshot of this dark picture. You can see some "dead pixels" on it. It casused by the hard X-ray radiation in the space. I dont know anything about this camera, but it seems, it has long time exposure on ISS to this X-ray radiations, and appeared on it some deffects on its pixel sensor.
On the attached picture the details are magnified by 400x zoom level, and you can see on top and left side a linea. Based on this here are the places of some dead pixels: 430x810, 490x825, 640x580 550x570, 670x835.
You can see this sensor deffects clearly in live stream, when the camera hasnot any light input.
I have the feeling, this dead pixels havenot too much similarities with the "fix" point on this recorded video, captured by the "nadir" HD camera: