The first row of the template in Migration Tool seems to be blank and if you try to execute the migration, you get errors in the Validation step saying "'General': Mandatory value missing in column 'ABC' ".
Obs: In this first row, there should be at least one column filled. It could be one of the last columns, so you can't see it in the Migration Tool unless you scroll to the side.
The XML file has one or more columns filled that are not related to the template and are probably a few rows after the template ends. The system is adding this row as a record, and since all other columns are empty, it is throwing the error of mandatory fields.
You need to clear this cell in the XML file and upload it again.