Steps to Reproduce
Load two users with different email addresses but the same user_name from LDAP.
Modify the user on LDAP.
Click Refresh from LDAP in the ServiceNow instance.
Note that only one user will get updated, and not necessarily the one on which you performed the action.
If email address is your unique identifier, map it to user_name in the transform map. For more information, see the product documentation topic Transform maps.
Related Problem: PRB635428