As a best practice, we recommend that the LDAP synchronization task parameter User Certificates be left blank.
This configuration might not be possible in specific cases when a hardware token that stores certificates in the AD is used at preboot authentication.
From the DE 7.x Best Practices Guide (PD24868):
User Certificate
The User Certificate attribute is used by the ePO Server to determine which certificate should be sent from ePO to the client, for example, smartcard tokens.
It's better to clear this attribute when you use the Password only token. Setting this attribute can accumulate a large amount of certificate data in the ePO database and impact LDAP performance; therefore, you can remove the certificate query from
DE LdapSync: Sync across users from the LDAP task while using the Password only token.
To overcome this issue, implement the workaround below.