Background: We had 2 Salesforce orgs and each org was connected to its corresponding Pardot Org. Recently, we merged the 2 Salesforce orgs. However, the pardot orgs were kept separate. So, now we have a single Salesforce org connected with 2 pardot orgs. Each pardot org caters to a separate line of business.
Issue: While merging, we migrated the contacts to the master org. These contacts now have new Salesforce ID. On the other hand, the prospects in Pardot org (which was connected to the deleted org) still has the old Contact Id. When these prospects try to sync with Salesforce, its unable to find the Contact and it tries to create a lead. But we have a duplicate rule that prevents from a new lead to be created if a contact exists with the same email address. This is causing sync issues in Pardot now.
What would be the best solution here? I am aware that we can't update the Contact ID in Pardot for the prospects.