UPN reverts to default in Active Directory

UCS - Univention Corporate Server
1

Hello,
I’m using the standard RSAT tools from Microsoft to manage my Univention LDAP. I’ve created an alternative UPN (@company.com) using Active Directory Domain & Trusts (to sync with O365 using entra connect).
All seemed to work, but recently I’ve noticed that users are randomly reverting to the default UPN (@company.internal). As I’ve learned in this topic, there are 2 objects for the UPN:

  • userPrincipalName
  • krb5PrincipalName

When I search my directory, I notice that userPrincipalName is using the @company.com suffix but krb5PrincipalName on the other hand is still using the @company.internal suffice.
Could it be a case that a sync between UCS & S4 is causing this behaviour? How could I make sure that this doesn’t happen anymore?

Kind regards