Sidhistory not migrated for few users only. 90% of the users had success Sidhistory migration.
Sidhistory migration adding the source objectsid to target Sidhistory attribute,
Not need to setup attribute mapping.
Have to select the box at template as shown the below screenshot:

N/A
Unmatch the account at environment page, and let the Workflow match it again and migrate the mapped attributes and Sidhistory.
Umatch:
