Thanks @PM490 for the observation! I think this is just sensor noise. It is highly unlikely that it is caused by the light source. The “light source” are three independent but identical light sources, driven by independent constant current sources. Any intensity variation would have to be sync’d with the line frequency of the camera. As this is a completely different circuit, I do not see any way how such a sync might happening.
This streaky noise pattern was discussed in the exposure fusion vs. raw capture thread and I have seen it in across the full frame (if that frame is dark enough) over the full area of the frame. It’s mainly present in the red channel, as this channel works with the highest overall gain of all color channels.
Usually spatio-temporal noise reduction gets rid of this noise.