ZIA SCIM synchronization error in Azure AD

Our IdP is configured with Azure AD using SCIM Auto-Provisioning. We synchronize 20k+ user accounts and several groups. I frequently notice a few errors in the Provisioning section of Azure AD for the configured ZIA enterprise application.

A further look at the audit and provisioning logs show the following -

Failed to update User ‘email@acme.com’ in ZscalerTwo

Sometimes the user account already exists in the Zscaler portal under User Management and curious to know why this is happening and the best way to fix. Performing a provisioning restart takes several hours to complete and the issue is not completely resolved.