Urgent SQL Magento 2 GDPR Issue

We recently migrated to a brand new magento 2 build and migrated all previous order data over from the old server to the new server, but now we have a major issue with random and old customer data i.e. addresses inside new user accounts.

I believe the issue is that new customer account ID's are conflicting with OLD customer account ID's, but I am unsure how this has happened or how to resolve it.