Sharepoint's People Picker doesn't work after Intra-forest Migration
Intra-forest migration with SID History applied to the target object confuses the Sharepoint People Picker. Only the target objects are visable. The Sharepoint server has not been processed with Resource Updating Manager, nor the Sharepoint Processing Wizard.
Even with the target objects disabled, and the "Disabled filter" set in People Picker, the source objects are not accessible
This prevents administrators from adding source objects to the Sharepoint Permissions.
Unless absolutely necessary, support recommends against migrating the SID history during Intra-forest migrations. Please see this article for further details.
Remove SID History from the target object