Welcome to LCOS and SXRD. I have described this at length in previous generations, spoke with JVC engineers about it back then, guess nothing has changed on this front.
What you are seeing is normal, no such thing as bright corners, just bad color uniformity. Some units are better, some worse. It's why I sold my original RS1 way back.
How long did you run exposure on the camera? If you can see this type of discoloration on your screen with hide option (O IRE window) I would try to get it exchanged if you can for a better unit.
Run through grey windows up to 50 IRE and look at color uniformity there, it usually changes at different IRE levels.
Now, if you want pure black at 0 IRE DLP is the only option.