It could be a faulty camera board - it does happen. Worth sending an email to Core, they’re pretty good at getting this stuff sorted (especially when you’ve had a decent go at some troubleshooting).
Absolutely, and if you reference this forum post in an email to support@coreelectronics.com.au then we should be able to reference this to speed up the troubleshooting process. Also, do you have any other Pi or cameras to cross check this against? The more references we can have to pinpoint this problem the better.