I'd say replace the solenoid. If the issue goes away when it's clean, then it could be something internally with the solenoid that clogs up or doesn't activate properly, so the code comes back.

 

For anyone else having 283d and 2845, I highly recommend having your car updated with ISTA/p. It took me forever to figure out the random vanos errors and there was nothing wrong with the car mechanically. Updating the car instantly fixed the issues and there's not a single problem now.