Getting UNWILLING_TO_PERFORM Error in API-Driven Inbound Provisioning for Active Directory

Getting error:

Error Code

HybridSynchronizationActiveDirectoryServiceAttributeExists

Error message

UnwillingToPerform-SvcErr: The server cannot handle directory requests. ResultCode: UnwillingToPerform, HResult: -2146233088Using APi-Driven Inbound Provisioning for Active Directory.

When I try to modify an attribute that is a custom schema extension in on-premises Active Directory, the provisioning agent throws the error. When the user is created, the attribute populates correctly. However, attempts to modify fail.This has all the characteristics of the agent trying to add a value instead of replacing. I do not know how to modify the provisioning agent's behavior. The attribute is defined as single value in the API-Driven schema. The definition values are identical to the displayName attribute, which updates without error. Michael Liben