AS3935 and register zero

The more I bang my head against this chip, the more I am certain there are ‘issues’ with it. I can now read and write every register with amazing repeatability except register zero. This register refuses to be read or written to. I have now crafted an email to the manufacturer asking them for help. Now I have already discovered one thing about this chip that leave me scratching my head how any competent engineer could have made such a stupid mistake. It would not surprise me that they also decided that register zero was off limits and yet claim full read write ability in the manual. So now I sit back and wait for an answer. Meanwhile, I am playing with my TE cooler. I can stabilize the temperature with a PID control loop. My only worry is that I think I am going to need a pretty big heat sink. More on this later.