OLAH Tim. Sorry heard that. It sounds really strange... Did you send it to an official Pioneer DJ technical support??
Maybe when they changed the wrong part they didn't find any error on that after test it.
Please contact again with your nearest Pioneer DJ technical support to secure you all process has been made corrdectly.
If the error persist, please make an inquiry from the link below. Then, you will be provided more detailed advice." https://rekordbox.com/en/support/inquiry.php
Take Care,
Pioneer DJ Forum support