Ok… sysinternals, specifically process monitor points to cubase writing over and over to …\Sonarworks\Sound ID Reference\Plugin\cfg.json. I do use the latest sonar works as a plugin in the control room.
As a test I disabled control room and the disk usage went from 100% to basically 0%. As soon as I re-enable the plugin the disk usage spikes right back up. So looks like there is an issue with the sonarworks sound id reference plugin when used as an insert in the control room.
Now the real question is if this is a sonarworks issue or a steinberg issue…