Magento 1.9.3.4 -> 2.1.8 data migration tool error

Question

I have tested steps of the import one at a time to determine that the issue occurs right after the map step. When I migrate customer and sales data using the data migration tool I get the following error during the Map step:

[WARNING]: Mismatch of entities in the document: 
catalogrule_product_price

[WARNING]: Volume Check failed

Another symptom that occurs after the Map step is the phone # and zipcode fields are missing from the checkout page.

Here is my config.xml:

<steps mode="data">
    <step title="Data Integrity Step">
        <integrity>Migration\Step\DataIntegrity\Integrity</integrity>
    </step>
    <step title="Customer Attributes Step">
         <integrity>Migration\Step\Customer\Integrity</integrity>
         <data>Migration\Step\Customer\Data</data>
         <volume>Migration\Step\Customer\Volume</volume>
    </step>
    <step title="Map Step">
         <integrity>Migration\Step\Map\Integrity</integrity>
         <data>Migration\Step\Map\Data</data>
         <volume>Migration\Step\Map\Volume</volume>
     </step>
     <!-- Issue Occurs Here -->
     <step title="OrderGrids Step">
         <integrity>Migration\Step\OrderGrids\Integrity</integrity>
         <data>Migration\Step\OrderGrids\Data</data>
         <volume>Migration\Step\OrderGrids\Volume</volume>
     </step>
     <step title="SalesIncrement Step">
         <integrity>Migration\Step\SalesIncrement\Integrity</integrity>
         <data>Migration\Step\SalesIncrement\Data</data>
         <volume>Migration\Step\SalesIncrement\Volume</volume>
     </step>
</steps>

Answer 1

A volume check fail is when there is a discrepancy between the number of rows in a source table and the number of rows in the destination table. Normally if a query fails the whole migration process should fail. If you did not temper with the migration tool. So this is likely caused by the fact that you had data on the M2 side going in the migration. When running a migration no data should be present on the M2 side except core Magento2 stuff(no sample data). This is stated in the docs as well.

It's also worth mentioning that there is a data-migration-tool version per each M2 version your are using.

I would also migrate directly to Magento 2.2.3 as upgrading from 2.1.8 to 2.2.2 or 2.2.3 after a migration was run is known to cause issues https://github.com/magento/data-migration-tool/issues/475

As for the missing attributes there a number of things that could've gone. If the values for those attributes were migrated successfully all you have to do is run a post-migration update script and set them to be used in the checkout form.

If the attributes were not migrated all together you have a problem on your hands. Maybe there were explicitly ignored or they conflicted with another existing attribute. A debugging process awaits you.