I'm posting this up quick while I'm thinking of it. The two images here don't illustrate this well at all. So I'll round up some better images later...
Working with my footage that shows the infamous "black sun" or dark grey / purple spot in bright flares, I'm able to recover information out of that dark spot. It behaves just like an error with some sort of clipping threshold. The threshold seems to be defined or influenced in relation to which ASA the RAW image is being "exposed" for. A higher ASA value appears to raise the threshold, lower ASA values lower it.
The "black sun" or sensor protect or whatever we call it, appears to be pixels that have exposure values extending beyond this limit or threshold. At this limit, instead of simply being left at a 100% luma value, it's as if they're being rolled-over to zero. Increasing the ASA seems to change that upper limit and much of the dark or black pixel data no longer "rolls over" (assuming that is what is happening) and it remains white or at a 100% luma value.
So I'm thinking that the "black sun" is completely fixable and may even be a bug in how the camera, REDCINE and RED Alert all interpret the RAW data as the anomaly is present in the camera outputs as well the software tools.
This image is a 1:1 crop showing a flare with slight "sensor protect" artifacting. Shot / exposed for ASA 320.
The exact same frame from the same R3D file, but exposed for ASA 400. The "sensor protect" artifacting has disappeared.