Domain prefix is missing in synced users (via MIM Integration) profiles in SharePoint 2016

Hey Techies, 

One of our customers facing a strange issue where SharePoint user profiles won't contain the domain prefix in the synchronized profiles. Microsoft Identity Manager (MIM) 2016 integration is in place for this environment and the connectors etc.. were provisioned as per the guidelines. 

Issue is similar to what's posted here but the workaround is fairly drastic. It deletes the accounts that are already created in the profile service - Wrong Domain Name in AccountName after User Profile Sync - Experiences of an Inland Empire Dad (iedaddy.com)

Any thoughts or suggestions are highly appreciated! 

Thank you!