I don't remember the meaning now, but Error 30 has a specific meaning. Have you checked what it's for? It's not like the Error 99, which mean anything you can't specify.
If I look in the log in the camera I have on the desk right now, it says that 2017-06-07 at 19:21, it suffered from a communication issue between lens and body. That's an error 01.
However, for the camera I have here, they just say that error 30 is something that prevented photography, but they still don't disclose exactly what. So it's perhaps just for internal use in the workshop.
The only big error I've had in the last few years was obvious. The camera got hit in the rear so the small display cracked and it didn't work at all. No error code needed, as it was extremely obvious what the problem was. They replaced the rear body part and some electronics inside, and then it works again.