Error message: X+0b4265-780478 Internal Failure (Bad Tag) () / 9

What you should see when you 'Sync data with Companies House':

The message means you have a valid web filling authentication code and that your company information is up to date. The 'Sync data with Companies House' button is at the top of your company details page.

What you may see if the company is dissolved:

If your company is dissolved, you may see the above error message when you click the sync button.

If you do see the above message, you will need to confirm the company has been dissolved by going on Companies House's public register. Enter the company number/name and you should see Dissolved next to the company.
Once confirmed, you can either leave the company in your account or remove it.

IMPORTANT: A dissolved company does not need a valid webfiling authentication code.