Import from CRM - Account Owner, Last Modifed ID and Created By ID issue

Import from CRM - Account Owner, Last Modifed ID and Created By ID issue

I am trying to import accounts from our previous CRM using the Setup --> Data Administration --> Migrate tool. I need to retain the Account Owner information, as well as Created By and Last Modified By users.

It appears that I am unable to set the Account Owner on any records through this method - it assigns my user as the owner on all Accounts, regardless of what is in the Account Owner field. I have tried the user's FirstName LastName, Email Address used to log in, and the actual internal ID that begins with zcrm_. However, I found that after the accounts are imported, I can import the same file through Accounts --> Import Accounts, selecting only the required fields and the Account Owner field using the user's Email Address as the value, and it will update the accounts to have the correct owner.

However, I have the same issue with the Last Modified ID and Created By ID fields - I have tried importing the accounts using all 3 possible username formats in those fields, and no matter what, it always sets my user for Last Modified By and Created By. Unfortunately, I can't use the same workaround for these fields as I could for the Account Owner, as neither of these fields is available through the Accounts --> Import Accounts method.

What am I doing wrong, and how do I get the correct user information into these fields?