Zend certified PHP/Magento developer

Problem with Data Migration Tool 2.3.3 column count mismatch

Running Data Migration tool and get this error:

In Mysql.php line 91:
SQLSTATE[21S01]: Insert value list does not match column list: 
1136 Column count doesn't match value count at row 1
when migrating `magento_sales_order_grid_archive` table.

Looking at the output of the error message and the query displayed, it looks like problems start to happen in the last couple of columns:

...
sales_order.customer_bal_total_refunded AS `refunded_to_store_credit`,
null AS `mailchimp_flag` FROM `sales_order`
...

where the mailchimp_flag field is being read as “null” and then I think it should include something like:

`sales_order.signifyd_guarantee_status` AS `signifyd_guarantee_status`

because when the field values are being inserted, the final two fields in the insert part are:

`mailchimp_flag` = VALUES(`mailchimp_flag`),
`signifyd_guarantee_status` = VALUES(`signifyd_guarantee_status`)

…but I don’t see any reference to either the mailchimp field nor the signifyed filed in the configuration xml files.

How can I fix this issue and more forward?

I don’t think either field is particularly important to have in the archived data as MailChump can be reimported/reexported and we don’t use Signifyed at all.

Also: Can anyone recommend a good book/tutorial for how to work with the data migration tool. What I’ve found is pretty high-level and not particularly helpful for me.